A total of 1,144 infertile women were treated by artificial donor insemination. Unsuccessful ovulation induction was found in 96 of these cases. The obese women (BMI: 28-36) had a relative risk of unsuccessful ovulation induction of 2.7 (95% confidence interval (CI) = 2.1-3.4) compared with women lower or normal body weight (BMI: 20-24). The effect was smaller in women with a BMI 25-27 or < 19 (relative risk (RR) = 1.4, 95% CI = 0.9-2.1 and 1.5, 95% CI = 0.8-2.5), respectively. During the AID treatment 412 pregnancies occurred. Pregnancy rate achieved by insemination was 28% (50 pregnancies per 178 cases, BMI 16-19), 42% (251/599, BMI 20-24), 33% (92/286, BMI 25-27), and 21% (19/81, BMI 28-36), respectively, in the different BMI groups.