A simple procedure is described for the extraction of unstable barbiturates, such as evipan and pentothal, from blood. It is suitable for use in the rapid, routine detn. of any type of barbiturate. The blood is acidified with NaH2PO4, dried with anhydrous Na2SO4, and extracted in a Soxhlet apparatus with ether-petroleum mixture. After purification of the extract by means of charcoal and MgO, the barbiturate is estimated by the color reaction with CoAc2 and iso-propylamine in chloroform. The observed maximum error for the recovery of not less than 1 mg. of various barbituric acids added to blood was 20%.