A high proportion of maternal deaths are caused by abortion, especially induced abortion. This cross-sectional study determined the prevalence of illegally-induced abortion prior to admittance and its associated risk factors in 8 maternity hospitals in Isfahan, Islamic Republic of Iran, during 2003–04. In confidential interviews with 417 women who attended the hospitals with abortion, 50 (12.0%) reported that it was illegally induced. These abortions had a significant correlation with fever, septic shock and septic abortion. Of all pregnancies, 35.0% were unwanted, and 27.1% of these were illegally-terminated by induced abortions. Unwanted pregnancy was one of the most important risk factors for induced abortion (OR = 8.84, 95% CI 4.36–17.92).