Background: Fixed drug eruption (FDE) is an uncommon adverse reaction to medications. Mucosal areas, particularly the male genitalia, are favored sites. To our knowledge, no study has investigated the causative agent(s) in FDE occurring on male genitals of Iranian patients. So, we conducted a study to determine the most common agents and areas of involvement in fixed genital drug eruption of male patients.Methods: Diagnosis of FDE was supported by a positive history and physical examination. Data including age, site of lesions, time interval between drug administration and FDE development was collected and analyzed.Results: The age range of the 36 male patients was 17 to 60 years with a mean age ± standard deviation of 36.1±10.9 years. The most common causative drug was co-trimoxazole in 33 patients (91.7%). In the genital area, the most frequent involved site was the glans penis in 22 patients (61.1%), followed by the penis shaft in 11 patients (30.6 %) and the scrotum in 2 patients (5.6%).Conclusion: The most common causative drug is co-trimoxazole and the most common site is the glans penis.