Although uterine perforation is a potentially life-threatening complication of curettage abortion, little is known about the risk factors associated with uterine perforation or how to prevent it. Using linear logistic regression, we analyzed 67,175 curettage abortions performed at 13 institutions in the United States from 1975 through 1978. The overall incidence of confirmed perforation was 0.9 per 1,000 abortions. Performance of the abortion by a resident rather than by an attending physician was a powerful risk factor for perforation (relative risk, 5.5; 95% confidence interval, 3.3 to 9.2). Use of Laminaria for dilation had a protective effect, although this effect was not statistically significant (relative risk, 0.17; 95% confidence interval, 0.02 to 1.2). Among factors beyond the control of the physician, advancement of gestational age and previous delivery were significant risk factors. Use of Laminaria and performance of the abortion by an attending physician considerably lowered the risk of uterine perforation.