N-Nitrosomethyl(2-hydroxypropyl)amine (NMHPA), N-nitrosomethyl(2-oxopropyl)-amine (NMOPA), N-nitrosomethyl(2,3-dihydroxypropyl)amine (NMD23HPA), N-nitrosobis(2-hydroxypropyl)amine (NDHPA), N-nitroso(2,3-dihydroxypropyl)(2-hydroxypropyl)-amine(ND23HPHPA), N-nitrosobis(2-acetoxypropyl)amine (NDAcPA) and N-nitroso-2,6-dimethylmorpholine (NDMMOR) were mutagenic in Salmonella typhimurium strain TA100 in the presence of liver 9000 X g supernatant (S9) from mice, rats, hamsters, rabbits and monkeys. N-Nitroso(2-hydroxypropyl)(2-oxopropyl)amine (NHPOPA) and N-nitrosobis(2-oxopropyl)amine (NDOPA) were mutagenic in strain TA100 without metabolic activation, and both compounds were further activated by animal liver S9. NMOPA and NMHPA were also mutagenic in the presence of lung S9 from these animals and in the presence of human lung or liver S9. Pancreatic S9 from any of the animals did not activate any of the nine N-nitrosamines to mutagens.