A selective and sensitive method was developed for the determination of volatile N-nitrosamines by gas chromatography (GC). After denitrosation of N-nitrosamines with hydrobromic acid, the resulting secondary amines were converted into their N-diethylthiophosphoryl derivatives and then measured by GC using a DB-1701 capillary column with flame photometric detection. The calibration graphs for N-nitrosamines in the range 0.05-1 nmol were linear and sufficiently reproducible for quantitative determination. This method was successfully applied to cigarette smoke samples without prior clean-up. N-Nitrosamines and secondary amines were completely separated by extraction with diethyl ether containing 25% 2-propanol. Overall recoveries of N-nitrosamines added to cigarette smoke samples were 83-110%. By using this method, N-nitrosamines in these samples could be determined without any interference from coexisting substances. Analytical results for the contents of N-nitrosamines and secondary amines in mainstream and sidestream smokes of several cigarettes are presented.