This article describes two methods for the determination of 1,4-butanediol and gamma-hydroxybutyrate in human plasma and urine using capillary gas chromatography. For 1,4-butanediol, plasma or urine samples (500 microl) were extracted by protein precipitation whereas for gamma-hydroxybutyrate, plasma or urine samples (500 microl) were extracted and derivatised with BF3-butanol. The compounds were separated on a Supelcowax-10 column and detection was achieved using a flame ionization detector. The methods are linear over the specific ranges investigated, accurate (with a percentage of the nominal concentration <109.8%) and showed intra-day and inter-day precision within the ranges of 5.0-12.0 and 7.0-10.1%, respectively. No interferences were observed in plasma and urine from hospitalized patients.