This multicenter, prospective, double-blind study compared the safety and efficacy of clindamycin and ciprofloxacin versus ceftriaxone and doxycycline in the treatment of outpatients with mild to moderate pelvic inflammatory disease (PID) diagnosed by laparoscopy. Samples taken from the endocervix, endometrium, and abdominal cavity before treatment and from the endocervix after treatment were cultured for aerobes, anaerobes, Neisseria gonorrhoeae, and Chlamydia trachomatis. Of the 138 patients enrolled, 131 were evaluable for efficacy. The most prevalent bacteria were streptococci, staphylococci, and Escherichia coli (among aerobes) and Bacteroides species and peptostreptococci (among anaerobes). N. gonorrhoeae was present in 2% (3) of the 131 evaluable patients, and C. trachomatis was in 11% (15). The clinical cure rate was 97% (65 of 67) in the clindamycin and ciprofloxacin group and 95% (61 of 64) in the ceftriaxone and doxycycline group. Side effects were similar in both groups. In conclusion, the two regimens for the outpatient treatment of mild to moderate PID were similarly effective and safe.