The levels of N-nitroso-bis(2-oxopropyl)amine (BOP) and its metabolites in the urine, blood, bile, and pancreatic juice were compared after ip and oral administration of BOP to Syrian golden hamsters to explain the differing organotropic tumor spectra resulting from treatment by these two routes. The levels of BOP and its metabolites N-nitroso(2-hydroxypropyl)(2-oxopropyl)amine (HPOP) and N-nitroso-bis(2-hydroxypropyl)amine in the urine, blood, bile, and pancreatic juice were generally less after oral administration than after ip administration. The results suggested that HPOP may be a proximate pancreatic carcinogen in hamsters administered BOP, inasmuch as it was the major metabolite in the blood and pancreatic juice after ip administration. However, the results did not indicate a mechanism for the increased incidence of bile duct tumors after oral administration of BOP.