Six N-nitroso compounds (N-nitrosodimethylamine, N-nitrosodiethylamine, N-nitrosodi-n-propylamine, N-nitroso-N-methylurea, N-nitrosopyrrolidine, and N-nitrosodi-n-butylamine) were tested in rats for liver DNA damaging activity by the alkaline elution technique. On molar basis their DNA damaging potency was found to decrease in the above order, and to vary over a 28-fold range. The elaboration of homogenous data available from literature showed that the carcinogenic potency of the 6 N-nitroso compounds varied over an 18-fold range, and that their mutagenic potency varied over a 490-fold range. Regression analysis indicated that correlation between carcinogenic and DNA damaging potencies was positive but at a low significance level, while the correlation between carcinogenic and mutagenic potencies was negative.