OBJECTIVE: This study was undertaken to determine the effects of human immunodeficiency virus 1 infection on the clinical presentation, severity, causal organisms, and response to ambulatory therapy of pelvic inflammatory disease. STUDY DESIGN: Women 18 to 40 years old with lower abdominal pain for <1 month were recruited. Participants underwent a standardized questionnaire, physical examination, screening for human immunodeficiency virus 1 and other sexually transmitted infections, and endometrial biopsy to detect plasma cell endometritis. Reevaluations were performed at 1 and 4 weeks to assess response to therapy. RESULTS: Among 162 women with adequate endometrial biopsy specimens 63 (39%) had histologically confirmed endometritis. Endometritis was more frequent among women who were seropositive for human immunodeficiency virus 1 than among women who were seronegative (odds ratio, 3.0; 95% confidence interval, 1.5-5.9). Infections with either Neisseria gonorrhoeae or Chlamydia trachomatis, or both, were least common and bacterial vaginosis was most common among human immunodeficiency virus 1-infected women with CD4 T-lymphocyte counts <400 cells/mu L (P < .04, P < .03, respectively). After oral antibiotic therapy, similar proportions of both women who were seropositive and women who were seronegative for human immunodeficiency virus 1 had a greater than or equal to 75% reduction in clinical severity score (81% vs 86%). CONCLUSION: Outpatient treatment of pelvic inflammatory disease was successful regardless of human immunodeficiency virus 1 serostatus.