Donor intrauterine insemination with washed spermatozoa (fresh semen) was performed in 36 women (63 cycles) whose husbands had azoospermia due to primary or secondary testicular failure. Simultaneously a control group of 76 couples (156 cycles) with proven fertility, who had recently discontinued mechanical non-hormonal contraception, were encouraged to have sexual intercourse during the fertile period. The age of the women was similar in both groups and the timing criteria were also similar. The pregnancy rate per woman was 50% in the donor insemination group and 47.4% in the control group (difference not significant). The pregnancy rate per cycle was 28.6% in the artificial insemination group and 23.1% in the control, natural insemination group (difference not significant). The number of artificial or natural insemination cycles required to achieve pregnancy was similar in the study and control groups. This study suggests that when the inseminating spermatozoa and female partner are normal, as occurs in the donor insemination group, intrauterine insemination is as efficient as natural insemination in achieving pregnancy but is not more successful.