Childhood cancer treatment can lead to infertility. Organ culture of early postnatal testicular tissue might provide a valuable approach to the study of acute testicular toxicity. The aim of the present study was to develop a functional in vitro organ culture method, in order to identify sensitive target cells to doxorubicin-induced cytotoxicity in immature rat testis during germ cell migration prior initiation of the first wave of spermatogenesis. Testicular tissue fragments from 5-day-old Sprague-Dawley rats were cultured in the absence or presence of doxorubicin (40 and 100ng/ml) and morphology, apoptosis, proliferation and testosterone secretion was analyzed. Postnatal testicular development proceeded normally in control samples for 48h in vitro. In these untreated culture conditions germ and Sertoli cell numbers and germ cell migration were comparable to in vivo. Germ cells were the primary, most sensitive targets for in vitro-induced doxorubicin (100ng/ml) toxicity and their death was not associated with any morphological defects in the Sertoli cells. Organ culture which reduces the need of animal experimentation can be used to study the cytotoxic effects of doxorubicin on the immature testis.