Background: The majority of chronic urticaria cases are chronic idiopathic urticaria (CIU) with no specific identifiable etiology. The role of autoantibodies in such cases remains controversial. Objective: This study determined the positivity rate of autologous serum tests in CIU patients. Methods: This study was performed on 30 patients with CIU and 30 individuals without any systemic or dermatologic disease. After the volar parts of right and left forearms were cleansed, 0.05 ml serum physiologic and 0.05 ml autologous serum were injected intradermally on the right forearm 5 cm apart from each other, resulting in the formation of small papules; meanwhile, 0.05 ml histamine alone was injected to the left forearm. The test results were evaluated after 30 minutes as positive in positive cases. Results: The autologous serum test produced significant and non-significant results in patients with CIU and controls, respectively. The positivity rates of the autologous serum test in the CIU and control groups were 53.3% and 26.6%, respectively. There was no relationship between autologous serum test positivity and sex in either group. In male patients with CIU, positive results ranged widely with age, while in female patients, positive results were mainly observed at younger ages with a narrow age range. Conclusion: The autologous serum test is a useful test in the diagnosis and treatment of CIU as well as the selection of immunotherapy, especially in patients refractory to classic therapy.