In order to investigate the transfer of nivalenol (NIV) and fusarenon-X (FX) from pregnant to fetal mice and from lactating to suckling mice, (3)H-NIV or (3)H-FX was given p.o. to pregnant or lactating mice. Radioactivity was detected in the whole fetal tissues as well as the fetal liver and kidney, the levels being comparable to those of the maternal tissues. Radioactivity was also detected in the milk, and liver and kidney tissues taken from suckling mice of both (3)H-NIV or (3)H-FX administered dams. HPLC analysis of fetal tissue homogenates from non-labeled FX- or NIV-administered pregnant mice revealed transmission of NIV to fetuses after administration of either toxin. In mice given the non-labeled FX, major and minor peaks of NIV and FX on HPLC were noted in suckling pup tissue homogenates. The results demonstrate that NIV transfers in unchanged form to fetal or suckling mice via placenta or milk, respectively, and that FX does so mainly after being metabolized to NIV in maternal body.