ABSTRACT The aim of the study was to determine whether rabbit eggs’attract’ homologous spermatozoa in vivo. Preliminary experiments showed that, in vitro, rabbit spermatozoa readily and irreversibly attach to the zonae of rat eggs. When rat and rabbit eggs were transferred into oviducts of previously mated rabbits, a significantly larger number of spermatozoa collected within the rabbit eggs than on the zonae of the rat eggs. Since the experiments were designed so that rat and rabbit eggs had equal chances of sustaining collisions with rabbit spermatozoa, the great preponderance of spermatozoa in the rabbit eggs suggests that the latter exert a chemotactic influence on rabbit spermatozoa.