A spectrophotometric method for the determination of N-nitroso compounds by flow injection analysis, based on a denitrosation reaction with hydrogen bromide - acetic acid followed by reaction of the liberated nitrite with the Griess reagent, is described. Under the optimum reaction conditions, the detection limit for N-nitrosopyrrolidine (NPYR) was 5 x 10^-8 M for a sample volume of 200 pl and the relative standard deviations (n = 9) for 1 x 10^-7 and 5.4 x 10^-6 M NPYR were 3.8 and 0.5%, respectively. Various other N-nitroso compounds gave a similar level of response. Phenol, sorbic acid and methanol did not interfere with the determinations, whereas piperazine interfered seriously with the determination of nitrosoproline. The sampling rate was 25 samples h-1. The method was successfully applied to the analysis of two anti-cancer drug formulations, viz., nimustine hydrochloride and l-(2-chloroethyl)-3-(methyl-alpha-D-glucopyranos-6-yl)-1-nitrosourea injections.