GC and UV/TLC procedures for barbiturate determinations yield clinically comparable analyses. Depending on the available personnel and equipment, one or the other may be used satisfactorily. When a large number of samples (20 or more) of barbiturate analyses are required, the described GC procedure is as reliable, but faster and more sensitive than the UV procedure. It involves extracting 1 ml of blood or urine with 5 ml of toluene containing aprobarbital as an internal standard. Any barbiturate in the toluene extract is then concentrated in 25 µl of 40% TMAH, an aliquot of which is injected into the gas chromatograph. The methylated barbiturates thus formed require 20 minutes for quantitative analysis.