Abstract 1. 1. Adult male rats were subjected to intraperitoneal (i.p.) saline (controls) or barbiturates (20 mg/rat) as a single injection. 2. 2. Seventeen hours later the rats were sacrificed and plasma collected. 3. 3. Hematocrit (HCT), Platelet count (PLT), prothrombin time (PT), partial thromboplastin time (APTT), and coagulant activity for factors II, V, VII, VIII, X and XII, plus fibrinogen were determined. 4. 4. The data indicates that a single injection of phenobarbital and secobarbital had a greater effect on clotting activity than did barbital or amobarbital. 5. 5. This was primarily reflected in the hepatic synthesized clotting factors, plus the platelets.