ABSTRACT: Ectopic pregnancy is a major health problem accounting for about 10% of all maternal mortality. To determine whether patients with a history of recurrent spontaneous abortion (RSA) have a higher frequency of ectopic pregnancy than the general population, the obstetrical histories of 630 patients with a diagnosis of RSA from two centers were studied. Thirty-eight of 376 USA women, (10%) and 10 of 193 British women (5%) previously had suffered an ectopic pregnancy. These data provide an overall prevalence of 9% for ectopic pregnancy among patients who recurrently abort. The total number of pregnancies was 1,716 in the USA group and in the British group was 1,270, for a total of 2,986 including live births, stillbirths, abortions, hydatidiform moles, and ectopic pregnancies. In the US series, 45 of the 1,716 pregnancies were ectopic. If these women had the same relative proportion of ectopic pregnancies as the general population, there should have been 20.6 ectopic pregnancies. This represents a 2.2-fold increase in patients with a history of RSA. There was no association between pregnancy order and occurrence of ectopic pregnancy. The prevalence of known risk factors for ectopic pregnancy in patients with a history of ectopic pregnancy was PID, 3%; tubal surgery, 20%; and used IUD, 3%. Seventy-four percent of the women had no identifiable risk factor. These results suggest a comorbidity for ectopic pregnancy and RSA which may indicate shared etiologies.