Two hundred eighty-one patients were available for follow-up after undergoing bilateral lower-extremity venous laboratory evaluations for possible deep-venous thrombosis. Because of a recognized difficulty with such a clinical diagnosis, the use of Doppler ultrasound and mechanical plethysmography with air-filled cuffs was carefully studied. Eighty-three of the 281 patients had confirmatory results from venography or fibrinogen scan of the symptomatic or more-symptomatic leg, and these 83 patients were used to determine accuracy. The complete evaluation as performed was accurate in 70% of the patients with suspected deep-venous thrombosis. The Doppler examination alone was accurate in 71% of the patients, and the maximum venous outflow measurement was accurate in 67% of the patients. This study indicates a continuing need for venography or fibrinogen scanning for the diagnosis of deep-venous thrombosis.