An analytical methodology was developed for the quantitative assay of phenobarbital, pentobarbital and butobarbital in blood samples, using aprobarbital as an internal standard. After sample cleaning by liquid-liquid extraction, the separation was achieved by liquid gas chromatography using a capillary column in pulsed splitless mode, temperature ramp, and helium as carrier gas and flame ionization detector. The methodology was selective, linear, precise and accurate. The linearity was adequate, between 20 and 100 mcg/mL, for all of three barbiturates studied. The developed methodology was applied in two forensic cases presented in the Toxicology lab of the National Institute of Legal Medicine and Forensic Sciences in Bogota.