A technique for timing hand revascularization utilizing the Allen test was standardized in 800 hands of 400 control subjects. The average timed radial artery fill was 2.4 +/- 1.2 seconds. The average ulnar artery fill was 2.3 +/- 1.0 seconds. Seven per cent of ulnar arteries and 2% of radial arteries did not fill completely within 6 seconds. Ninety-one per cent of the hands tested were considered complete with uniform brisk refill. The clinical observation of inadequate or absent revascularization correlated with reduced digital blood pressure. For the test to be accurate and reproducible at least 11 pounds of digital pressure are necessary to uniformly occlude both arteries and reduce the digital blood pressure to 0 mm Hg.