To evaluate the usefulness of the template bleeding time post-aspiring ingestion, this test was performed with other tests of haemostasis in 28 controls and 71 patients. The mean bleeding time (B.T.) in 24/28 true controls was 3.5 +/- 1 min (1 SD). Following the ingestion of 600 mg aspirin the B.T. was 6.3 +/- 1.4 min. Four out of 28 false 'controls' with negative bleeding histories were documented to have asymptomatic von Willebrand's disease and abnormal post-aspirin B.T. Of the 71 patients studied, 22 had initial B.T. that were abnormal (16 with classical von Willebrand's disease and six with platelet dysfunction). Of the remaining 49 patients with initially normal B.T., 30 had abnormal post-aspirin B.T. Of these 30 patients 13 had von Willebrand's disease. In eight, initially the abnormal B.T. post-aspirin was the only abnormality demonstrable but later they were shown to have von Willebrand's disease. In four the abnormal post-aspirin B.T. was combined with abnormal Ristocetin aggregations and a positive family history. These patients were presumed to have a variant of von Willebrand's disease. The remaining five had platelet dysfunctional states. Of the 19 patients with normal initial post-aspirin B.T., 16 demonstrated no haemostatic abnormality, and three were proven to have von Willebrand's disease. The aspirin tolerance test raised the sensitivity of the B.T. as a screening test for haemostasis from 40% to 94% in the abnormal patient population.