Objective: To evaluate whether acupuncture pretreatment followed by letrozole leads to a higher live birth rate in PCOS when compared with letrozole alone. Design: Multicenter randomised controlled trial. Setting: Three hospitals in China. Population or Sample: Anovulatory women with PCOS aged from 20 to 40 years who had at least one patent tube. Methods: Participants were randomly assigned to receive acupuncture pretreatment followed by letrozole (pretreatment group) or letrozole alone (control group). Acupuncture pretreatment was given three times per week for 16 weeks, and letrozole was given five days per cycle for up to four cycles. Main outcome measures: The cumulative live birth rate (defined as a delivery after 20 weeks’ gestation). Results: The cumulative live birth rate was 41.1% (79/192) in the pretreatment group and 34.4% (66/192) in the control group with no significant difference between groups but was significantly higher in the pretreatment group (48/98, 49.0%) among those with baseline HOMA-IR <2.14, when compared with the control group (19/66, 28.8%). No significant differences were found between groups stratified by the letrozole cycle number, body mass index, age, PCOS phenotype, or hyperandrogenism. Conclusions: Acupuncture pretreatment followed by letrozole did not increase the cumulative live birth rate of anovulatory women with PCOS when compared with letrozole alone but may increase the cumulative live birth rate in those whose baseline HOMA-IR is <2.14. Key words: acupuncture, letrozole, live birth, PCOS, pretreatment