Automated procedures involving a chromogenic substrate sensitive to thrombin-sarcosine-Pro-Arg p-nitroanilide were compared with conventional tests for prothrombin times and activated partial thromboplastin times (APTT) and with specific assays for factors V, VII, VIII, IX, X, XI, and XII. The reproducibility and sensitivity of the chromogenic tests were compared with those of the clotting tests. Further, we have confirmed that the chromogenic test for APTT is sensitive to factor VII deficiency, unlike the clotting test for APTT. This might be an advantage in monitoring orally anticoagulated patients. The ready availability of the automated equipment for performing the chromogenic tests suggests their potential for routine use. However, some discrepant results in certain patients with liver disease and in others with factor VIII inhibitors warrant caution.