Background: Misoprostol is a prostaglandin El analogue that has been used for medical abortion. We conducted this prospective study to compare the efficacy of vaginal misoprostol for abortion in women at a gestational age of <42 days and in women at a gestational age of 42-56 days. Methods: A total of 160 women seeking medical termination of a pregnancy of <56 days were enrolled in the study. Medical termination was performed using 800 mug of vaginal misoprostol, repeated every 24 h for a maximum of three doses. Results: The overall complete abortion rate was 91.3%. In group A (gestation <42 days) complete abortion occurred in 96.3% of women, whereas in group B (gestation=42-56 days) complete abortion occurred in 86.3% of women (P<0.025). The two groups did not differ significantly with respect to side-effects (incidence of pain, bleeding, nausea, diarrhoea, fever and headache). Women who had aborted successfully were significantly more satisfied with the method compared with women who did not (P<0.001). Conclusions: The vaginal misoprostol-alone regimen is highly effective for women seeking medical abortion of pregnancies of <= 56 days. However, better efficacy may be achieved at a gestational age of <42 days.