Before the advent of the electron capture detector, we were unable to apply the efficient separating ability of gas chromatography to the minute quantities of polynuclear aromatic hydrocarbons reported to be present in cigarette smoke. Now, however, with properly chosen operating conditions, the electron capture detector will respond to less than 0.02 microgram of most of the polynuclears. Good separation of known polycyclics was obtained on a gas chromatographic unit, using a silicone rubber column. As little as 0.01 microgram of benzo(a)pyrene and corresponding amounts of the other polycyclics could be detected. The electron capture detector response was a linear function of concentrations of amounts less than one microgram, making quantitative measurements possible.