We compared the effectiveness of 2 treatment regimens for isoniazid-resistant tuberculosis (TB) in 42 patients attending a TB referral centre in the Islamic Republic of Iran. The patients were divided into 2 treatment groups: 26 received the 6-month standard HRZE treatment and 16 received a modified treatment of RZE for 6 months. There were no significant differences in age or sex of the groups. With the standard method of treatment, 21 (80.8%) patients were cured, 4 (15.4%) resulted in treatment failure, and 1 (3.8%) died. In the modified treatment group, 16 (100%) patients were cured, These differences were not statistically significantly different (P = 0.194).