OBJECTIVE The purpose of this study was to compare the efficacy of a 3-day course of doxycycline to a standard 7-day course for treating uncomplicated chlamydia cervicitis. METHODS During an 18-month period, 77 women with uncomplicated chlamydia cervicitis were randomized to receive either a 3-day or a 7-day course of doxycycline (100 mg twice daily). Tests of cure were performed 3 weeks after completion of therapy with the Amplicor polymerase chain reaction (PCR) assay (Roche Molecular Systems, Branchburg, NJ). Demographics, therapeutic results, and side effects for the two groups were compared. RESULTS Seventy-three patients completed the study: 35 in the 3-day group and 38 in the 7-day group. There were no significant differences in age, gravidity, or parity between the groups. There was a 94% (33/35) cure rate in the 3-day group and a 95% (36/38) cure rate in the 7-day group (P = 1.0). Thirty-four percent and 32% of the patients in the 3- and 7-day groups reported side effects, respectively; there was no significant differences between the 3- and 7-day groups in regard to population demographics, patient compliance, therapeutic outcome, or side effects. CONCLUSIONS A 3-day course of doxycycline appears to be as effective as a 7-day course of doxycycline for the treatment of uncomplicated chlamydia cervicitis.