The conventional plasma recalcification test is improved by incubation of test plasma with Celite suspended in distilled water. This effectively activates factor XII and releases platelet factor 3, thereby markedly shortening the clotting time. The modified plasma recalcification test has several advantages that contribute to its usefulness as a general screening test for coagulation abnormalities. It is more precise and reproducible than any comparable test that assays a similar spectrum of coagulation factors.