AbstractEctopic pregnancy in the fallopian tube occurs in about 1 in 50 human pregnancies. Maternal factors in the etiology of this condition have been well documented. There is less information available on the development of the embryo or fetus. To document this information morphological and cytogenetic data were obtained from 76 embryos and fetuses obtained from pregnancies occurring in the fallopian tube. Analysis of the data showed that tubal implantation was associated with a high proportion of severely disorganized embryos. There was also a high incidence of maternal tubal disease. The importance of these factors and the etiology of ectopic pregnancy is discussed.