Gas chromatographic methods may be used for the separation of many drugs and drug metabolites for purposes of identification or estimation. The most useful technics involve the use of columns with relatively thin films of thermostable liquid phases coated on inert or inactivated supports, and used with high-sensitivity detectors. Classes of compounds which may be studied include barbiturates, quinolines used as antimalarials, and phenothiazines and diphenylamines.