A rapid method for the gas chromatographic determination of barbiturates in biological samples has been developed. It consists of methylating the barbiturates with dimethyl sulfate, extracting the sample withn-heptane, and gas chromatographic analysis of the heptane extract on a SE-52 column. A preliminary study revealed that the method could be used forin vivoand/orin vitrodeterminations. Minimum detectable amounts of barbiturates were shown to be between 0.01 and 0.05 μg. An added advantage of the procedure is the lack of interference from other constituents which might be present in the analytical sample.