This review of the longterm impact of induced abortion on reproductive function includes a comprehensive survey of the published and the preliminary literature. Over 200 anecdotal, descriptive, and observational epidemiologic reports were reviewed, and more than 150 studies in 11 languages from 21 countries that employed 1 of 4 standard research designs were identified. With these investigations as the foundation, the influence of induced abortion on secondary infertility, ectopic pregnancy, spontaneous abortion, shortened gestation, low birth weight, complications of pregnancy or delivery, and infant outcome were evaluated. The data from each of these investigations were systematically reexamined. In cases where the data were incomplete, additional information was requested from the authors. These studies were categorized by such factors as their research design, the type of abortion procedure used, and whether potential confounding variables were considered. To compare the relative power of studies, the 95% confidence interval around the point estimate of relative risk was calculated where possible. Studies that failed to consider the many confounding factors associated with both induced abortion and adverse pregnancy outcome were of limited value because women who obtain induced abortions differ substantially from those who do not. Results from these studies usually indicated a higher risk estimate than results from better designed, controlled investigations. Relying more heavily on the latter, the following were among the findings: 1) secondary infertility, which may be a rare late effect of a complicated abortion, occurs so infrequently that its risk is not significantly elevated, even in studies capable of detecting a 2-fold rise in relative risk; 2) ectopic pregnancy, which also may be a rare late effect of an abortion complicated by infection or trauma, occurs so infrequently that its risk is not significantly elevated in studies capable of detecting a 2-fold rise in relative risk; 3) midtrimester spontaneous abortion is not more frequent for women who have experienced 1 previous abortion than for women who are in their 1st pregnancy; 4) shortened gestation in pregnancies after 1 induced abortion has an incidence similar to that in 1st pregnancies; 5) low birth weight is more frequent in 1st births after abortion performed by dilatation and curettage under general anesthesia, but it is not more frequent in 1st births after abortions performed by other methods, when compared with 1st pregnancy births; 6) 1 induced abortion does not protect a woman from the higher risks of low birth weight and pregnancy complications associated with a 1st birth; 7) repeat induced abortion has not been studied sufficiently to clarify whether the increased risks associated with it in some studies are caused by confounding factors or the procedures performed; and 8) 1st born infants whose mothers had 1 induced abortion are at similar risk of morbidity and infant mortality as other 1st born children.