The absorption, distribution and excretion of radioactivity was studied in groups of four male Wistar rats following a single dermal and intradermal administration of 19 Methylenebisphenylisocyanate ('C-MDI) at naminal dose levels of 4.0 and 0.4 mg/cm for dernal administration and 0.4 mg/animal for intradermal administration. These dose levels nomina:11y corresponded to 40 and 4.0 mg/animal for dermal administration. Considering the animal weights, dose levels corresponded to about 140 and 14 mg/kg body weight (dermal administration) and 1.4 mg/kg body weight (intradermal administration). In the experiments with dermal administration, animals were exposed for 8 hours and sacrificed 8, 24 or 120 h after beginning of exposure. In the experiment with intradermal administration, animals were sacrificed 120 h after treatment. After dermal administration of 'C-MDI, mean recoveries of radioactivity from all dose groups were in the range from 97.86 to 108.07 % of the total radioactivity administered. Generally, the largest proportion of.radioactivity was found at the application site and dressing. The total amount of radioactivity absorbed (including excreta, cage wash, tissues/organs and carcass) increased with increasing sacrifice time. Dermal absorption was very low and quantitatively similar at both dose levels; maximally ca. 0.9 % of the applied radioactivity was absorbed.