1. A method for the determination of N-ethyl-N-methylaniline and its metabolites by g.l.c. is described. 2. Following incubation in N-ethyl-N-methylaniline with rabbit liver microsomes for 60 min, over 95% of the substrate was accounted for as unchanged compound or metabolites. 3. N-Ethyl-N-methylaniline is metabolized in vitro by rabbit tissues mainly by N-oxidation and N-demethylation and to a lesser extent by N-deethylation and di-dealkylation. 4. Both major routes of metabolism were observed in homogenates prepared from rabbit liver and lung; in addition N-oxidation occurred in kidney and bladder tissue homogenates.