Carcinogenic action of dimethylnitramine (DMNO), diethylnitramine (DENO), and dibuthylnitramine (DBNO) on various animal species was studied. 200 ppm of DMNO in tap water induced no tumours in outbred rats, while DBNO induced hyperplastic lesions on the urinary bladder and DENO produced liver tumours in 2 of 5 rats. DMNO dissolve in aquarium water at a dose of 5 ppm induced tumours (kidney and liver adenocarcinomas and hemocytoblastosis) in 18 out of 40 and 6 out of 18 frogs respectively. Another amphibian species, Xenopus, showed similar sensitivity to DMNO action: hepatocellular cancers, cholangiocarcinomas and kidney tumours were found in 6 out of 14 animals and in another group, in 6 out of 17 animals treated with 400 ppm of DMNO dissolved in aquarium water. Few neoplasms were observed in experiments on fish (guppies zebrafish) and freshwater mollusks treated with DMNO and DENO. The carcinogenic effect of nitramines, appears to be much lower than that of related nitrosamines.