Five hundred three patients were accepted for the in vitro fertilization (IVF) program from 1983 to 1986. Two hundred ninety-nine patients had a total of 678 IVF treatment cycles during this period. Eighty-one clinical pregnancies resulted, of which 8 were ectopic pregnancies and 19 spontaneous abortions (group A). During this period 82 patients accepted for IVF became pregnant spontaneously: 44 before treatment and 38 after a failed IVF treatment cycle (group B). Of these, 14 were ectopic pregnancies and 8 were miscarriages. The main indications for acceptance on the IVF program were similar in the two groups if those patients who had a bilateral salpingectomy are excluded from group A. Causative factors for the high ectopic pregnancy rate are discussed. The authors suggest that after embryo transfer, migration of the embryo or embryos into the fallopian tubes occurs more frequently than realized, and the diseased tube is less likely than a normal tube to propel the embryo back into the uterus. The abortion rate in group B was similar to the rate in the general population.