diff --git a/.gitignore b/.gitignore
index 9ada4d7..660ad3d 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,2 +1,3 @@
 .idea
 /release
+coverage.txt
diff --git a/client_test.go b/client_test.go
index 5ceca6b..d8cfe4e 100644
--- a/client_test.go
+++ b/client_test.go
@@ -5,6 +5,7 @@ import (
 	"net/http"
 	"net/http/httptest"
 	"sort"
+	"sync"
 	"testing"
 
 	"github.com/sparetimecoders/goamqp"
@@ -332,3 +333,285 @@ func TestPrivilegeHandler_Fetch_Valid(t *testing.T) {
 	}
 	assert.Equal(t, expectedPrivileges, handler.privileges)
 }
+
+func TestPrivilegeHandler_Fetch_Concurrent_Fetches(t *testing.T) {
+	privileges := `
+{
+  "jim@example.org": {
+    "00010203-0405-4607-8809-0a0b0c0d0e0f": {
+      "admin": false,
+      "company": true,
+      "consumer": false,
+      "time": true,
+      "invoicing": true,
+      "accounting": false,
+      "supplier": false,
+      "salary": true
+    }
+  }
+}`
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		_, _ = w.Write([]byte(privileges))
+	}))
+	defer server.Close()
+
+	baseURL := server.Listener.Addr().String()
+	handler := New(WithBaseURL(fmt.Sprintf("http://%s", baseURL)))
+
+	// Run multiple Fetch calls concurrently to test thread-safety
+	var wg sync.WaitGroup
+	errors := make(chan error, 10)
+
+	for i := 0; i < 10; i++ {
+		wg.Add(1)
+		go func() {
+			defer wg.Done()
+			if err := handler.Fetch(); err != nil {
+				errors <- err
+			}
+		}()
+	}
+
+	wg.Wait()
+	close(errors)
+
+	// Check no errors occurred
+	for err := range errors {
+		assert.NoError(t, err)
+	}
+
+	// Verify privileges were set correctly
+	expectedPrivileges := map[string]map[string]*CompanyPrivileges{
+		"jim@example.org": {
+			"00010203-0405-4607-8809-0a0b0c0d0e0f": {
+				Admin:      false,
+				Company:    true,
+				Consumer:   false,
+				Time:       true,
+				Invoicing:  true,
+				Accounting: false,
+				Supplier:   false,
+				Salary:     true,
+			},
+		},
+	}
+	assert.Equal(t, expectedPrivileges, handler.privileges)
+}
+
+func TestPrivilegeHandler_Concurrent_Fetch_And_Read(t *testing.T) {
+	privileges := `
+{
+  "jim@example.org": {
+    "abc-123": {
+      "admin": true,
+      "company": true,
+      "consumer": false,
+      "time": false,
+      "invoicing": false,
+      "accounting": false,
+      "supplier": false,
+      "salary": false
+    }
+  }
+}`
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		_, _ = w.Write([]byte(privileges))
+	}))
+	defer server.Close()
+
+	baseURL := server.Listener.Addr().String()
+	handler := New(WithBaseURL(fmt.Sprintf("http://%s", baseURL)))
+
+	var wg sync.WaitGroup
+	errors := make(chan error, 100)
+
+	// Start multiple Fetch operations
+	for i := 0; i < 10; i++ {
+		wg.Add(1)
+		go func() {
+			defer wg.Done()
+			if err := handler.Fetch(); err != nil {
+				errors <- err
+			}
+		}()
+	}
+
+	// Concurrently read privileges while Fetch is running
+	for i := 0; i < 50; i++ {
+		wg.Add(1)
+		go func() {
+			defer wg.Done()
+			_ = handler.CompaniesByUser("jim@example.org", func(privileges CompanyPrivileges) bool {
+				return privileges.Admin
+			})
+		}()
+	}
+
+	// Concurrently check privileges while Fetch is running
+	for i := 0; i < 50; i++ {
+		wg.Add(1)
+		go func() {
+			defer wg.Done()
+			_ = handler.IsAllowed("jim@example.org", "abc-123", func(privileges CompanyPrivileges) bool {
+				return privileges.Admin
+			})
+		}()
+	}
+
+	wg.Wait()
+	close(errors)
+
+	// Check no errors occurred
+	for err := range errors {
+		assert.NoError(t, err)
+	}
+
+	// Verify privileges are correct after all concurrent operations
+	companies := handler.CompaniesByUser("jim@example.org", func(privileges CompanyPrivileges) bool {
+		return privileges.Admin
+	})
+	assert.Equal(t, []string{"abc-123"}, companies)
+
+	isAllowed := handler.IsAllowed("jim@example.org", "abc-123", func(privileges CompanyPrivileges) bool {
+		return privileges.Admin && privileges.Company
+	})
+	assert.True(t, isAllowed)
+}
+
+func TestPrivilegeHandler_Concurrent_Process_And_Read(t *testing.T) {
+	handler := New(WithBaseURL("base"))
+
+	var wg sync.WaitGroup
+
+	// Concurrently add privileges via Process
+	for i := 0; i < 100; i++ {
+		wg.Add(1)
+		companyID := fmt.Sprintf("company-%d", i%10)
+		go func(id string) {
+			defer wg.Done()
+			_, _ = handler.Process(&PrivilegeAdded{
+				Email:     "jim@example.org",
+				CompanyID: id,
+				Privilege: PrivilegeAdmin,
+			}, goamqp.Headers{})
+		}(companyID)
+	}
+
+	// Concurrently read privileges while Process is running
+	for i := 0; i < 100; i++ {
+		wg.Add(1)
+		go func() {
+			defer wg.Done()
+			_ = handler.CompaniesByUser("jim@example.org", func(privileges CompanyPrivileges) bool {
+				return privileges.Admin
+			})
+		}()
+	}
+
+	wg.Wait()
+
+	// Verify all companies were added
+	companies := handler.CompaniesByUser("jim@example.org", func(privileges CompanyPrivileges) bool {
+		return privileges.Admin
+	})
+	sort.Strings(companies)
+
+	expected := make([]string, 10)
+	for i := 0; i < 10; i++ {
+		expected[i] = fmt.Sprintf("company-%d", i)
+	}
+	sort.Strings(expected)
+
+	assert.Equal(t, expected, companies)
+}
+
+func TestPrivilegeHandler_Concurrent_Multiple_Operations(t *testing.T) {
+	privileges := `
+{
+  "jim@example.org": {
+    "initial-company": {
+      "admin": true,
+      "company": true,
+      "consumer": false,
+      "time": false,
+      "invoicing": false,
+      "accounting": false,
+      "supplier": false,
+      "salary": false
+    }
+  }
+}`
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		_, _ = w.Write([]byte(privileges))
+	}))
+	defer server.Close()
+
+	baseURL := server.Listener.Addr().String()
+	handler := New(WithBaseURL(fmt.Sprintf("http://%s", baseURL)))
+
+	var wg sync.WaitGroup
+
+	// Fetch
+	for i := 0; i < 5; i++ {
+		wg.Add(1)
+		go func() {
+			defer wg.Done()
+			_ = handler.Fetch()
+		}()
+	}
+
+	// Process PrivilegeAdded
+	for i := 0; i < 20; i++ {
+		wg.Add(1)
+		go func(idx int) {
+			defer wg.Done()
+			_, _ = handler.Process(&PrivilegeAdded{
+				Email:     "jane@example.org",
+				CompanyID: fmt.Sprintf("company-%d", idx%5),
+				Privilege: PrivilegeCompany,
+			}, goamqp.Headers{})
+		}(i)
+	}
+
+	// CompaniesByUser reads
+	for i := 0; i < 50; i++ {
+		wg.Add(1)
+		email := "jim@example.org"
+		if i%2 == 0 {
+			email = "jane@example.org"
+		}
+		go func(e string) {
+			defer wg.Done()
+			_ = handler.CompaniesByUser(e, func(privileges CompanyPrivileges) bool {
+				return privileges.Admin || privileges.Company
+			})
+		}(email)
+	}
+
+	// IsAllowed reads
+	for i := 0; i < 50; i++ {
+		wg.Add(1)
+		go func() {
+			defer wg.Done()
+			_ = handler.IsAllowed("jim@example.org", "initial-company", func(privileges CompanyPrivileges) bool {
+				return privileges.Admin
+			})
+		}()
+	}
+
+	wg.Wait()
+
+	// Verify final state is consistent
+	jimCompanies := handler.CompaniesByUser("jim@example.org", func(privileges CompanyPrivileges) bool {
+		return privileges.Admin
+	})
+	assert.Contains(t, jimCompanies, "initial-company")
+
+	janeCompanies := handler.CompaniesByUser("jane@example.org", func(privileges CompanyPrivileges) bool {
+		return privileges.Company
+	})
+	sort.Strings(janeCompanies)
+
+	expectedJane := []string{"company-0", "company-1", "company-2", "company-3", "company-4"}
+	assert.Equal(t, expectedJane, janeCompanies)
+}