This study investigated the impact of women's body mass index (BMI) on the outcome after consecutive IVF/intracytoplasmic sperm injection cycles in 487 patients initiating treatment with 5-year follow-up. The total number of cycles was 1417. In total 103 (21.1%) were overweight (BMI 25-29.9 kg/m²) and 59 (12.1%) were obese (BMI ≥ 30 kg/m²). Number of initiated cycles/woman (P=0.01), number of cancelled cycles/woman (P <0.01) and the total dose of gonadotrophin used/cycle (P <0.01) rose with increasing BMI. A negative linear association between BMI and the number of retrieved oocytes (B=-0.243, P <0.001) and an inverse U-shaped relationship between BMI and the number of developed embryos was seen, with less embryos available among underweight and obese women (P=0.03). The number with positive serum human chorionic gonadotrophin/cycle decreased significantly with increasing BMI (P <0.01). The ongoing pregnancy rate/cycle among the obese women was lower (20.8% versus 28.3% in normal-weight women; P=0.04). Live-birth rate per cycle was 15.2% versus 21.5%. Multiple logistic regression analysis showed that the only independent predictors of live birth were women's age (P=0.037), women's BMI (P=0.034) and men's age (P=0.040).