To compare the effectiveness of amoxicillin and erythromycin for the treatment of antenatal Chlamydia trachomatis infection by meta-analysis of available trials involving random assignment of subjects. A computer search of English-language abstracts using MEDLINE and the Cochrane Pregnancy and Childbirth Database (medical subject heading terms: pregnancy, chlamydia, erythromycin, amoxicillin, antenatal antibiotics) was supplemented with a review of the bibliographies of the relevant articles generated by the computer search. Five trials were identified, four of which met our inclusion criteria for the metaanalysis. Trials to be included in this meta-analysis underwent trial quality evaluation and data abstraction. An estimate of the relative risk (RR) was calculated for the dichotomous outcomes using a fixedeffects model. The pooled RR for the effectiveness of amoxicillin compared with erythromycin was 1.11 (95% confidence interval [CI]1.05–1.18), and the pooled RR for gastrointestinal side effects of amoxicillin compared with erythromycin was 0.29 (95% CI 0.20–0.42). The pooled RR for gastrointestinal side effects that resulted in discontinuation of therapy of amoxicillin compared with erythromycin was 0.14 (95% CI 0.06–0.36). The available data suggest that amoxicillin is more effective than erythromycin for the treatment of antenatal C trachomatis infection and has fewer gastrointestinal side effects, leading to better compliance.