Four patients with hypothenar hammer syndrome were evaluated preoperatively with Doppler mapping and angiography. Both tests documented ulnar artery occlusion. In one patient, the proximal extent of thrombosis could not be identified by angiography. In all cases Doppler mapping accurately documented the extent of occlusion as confirmed by surgical exploration. Doppler mapping is a noninvasive alternative to angiography in the evaluation of hypothenar hammer syndrome.