The pharmacokinetics of N-nitrosodimethylamine was studied in patas monkeys following i.v. doses of 0.5, 1.0, and 5.0 mg/kg and a p.o. dose of 1.0 mg/kg, and in Swiss mice at i.v. doses of 1.0 and 2.0 mg/kg. In the patas monkey the pharmacokinetics was linear over the i.v. dose range studied. The mean clearance (Cl), steady-state volume of distribution (Vss), mean residence time, and elimination half-life (t 1/2) were 103.3 +/- 26.7 (SD) ml/min, 3061 +/- 821 ml, 30.8 +/- 10.8 min, and 21.1 +/- 8.5 min, respectively. Assuming that the pharmacokinetics was linear at the p.o. dose used, the p.o. bioavailability of N-nitrosodimethylamine in the monkey was 49%. The pharmacokinetics was also linear in mice, and the average Cl, Vss, mean residence time, and t 1/2 were 3.81 ml/min, 21.0 ml, 5.5 min, and 11.9 min, respectively. These data and data for rats, hamsters, rabbits, dogs, and pigs taken from the literature were used to scale Cl and Vss to body weight using the allometric equation. The resulting equation for Cl was Cl = 49.7B0.998 and the equation for Vss was Vss = 748B1.05 where B is body weight in kg. The fit of the data to the equation was excellent in both cases. Using these equations and assuming a body weight of 70 kg for humans, the Cl and Vss for N-nitrosodimethylamine in humans are estimated to be 3450 ml/min and 64,800 ml, respectively.