This randomized controlled trial investigated whether delaying human chorionic gonadotrophin hormone (hCG) administration within an IVF cycle impacts upon clinical outcomes. Participants included 125 women undergoing IVF/ICSI cycles at Leeds Centre for Reproductive Medicine. Subjects were aged 20-36 years, body mass index (BMI) 20-30 kg/m(2) with a normal FSH level (<8 IU/l). Administration of hCG took place 35-36 h prior to oocyte retrieval when there were ≥3 follicles ≥17 mm in diameter (Group A), delayed by 1 day (Group B) or 2 days (Group C). Outcomes included the number of oocytes retrieved per cycle, fertilization rate and live birth rate. On the day of oocyte retrieval, women in Groups B and C had significantly more mature follicles than Group A, although the number of oocytes retrieved did not differ (median = 12 in each group). Fertilization rates and embryo quality were comparable between groups. Pregnancies and live births per cycle were higher in Groups B and C (A = 30.8%, B = 54.1%, C = 38.7%; A = 17.9%, B = 27.0%, C = 25.8%), but did not reach statistical significance. Delaying hCG administration had no significant negative impact upon morphological quality of embryos, availability of surplus embryos for freezing or pregnancy outcomes. Postponing hCG may enable increased flexibility of cycle scheduling to avoid weekend procedures.