Three hundred consecutive women with the surgical and histological diagnosis of ectopic pregnancy were studied to evaluate the etiological factors associated with this problem. Seventy-seven women had a history of surgical evidence of pelvic inflammatory disease (PID); 46 had a history of abdominal pelvic surgery; 32 had a history of both PID and surgery. Forty-three women had used an intrauterine device (IUD), and 32 had a device in utero at the time of the ectopic pregnancy. However, no definite relationship between use of the IUD and ectopic pregnancy could be established. A pregnancy test was positive in 207 of the 251 women on whom it was performed. Culdocentesis, performed on all patients, yielded nonclotting blood in 285 patients. Hematocrit value, measured on the culdocentesis specimen, was greater than 15% in 278 of the 285 women.