Thirty patients seen following frostbite injury during a 2-week period were treated with rapid rewarming in a saline bath. Vascular laboratory evaluations including digital plethysmograms and Doppler ultrasound mapping of digital vessels and distal palmar and pedal arches revealed three general degrees of vascular response to cold injury after rewarming. The most common, the hyperdynamic response, implying patent digital vessels, was often clinically apparent, with warm, red digits. Regional sympathectomy may be troublesome in these patients. Patients without a hyperdynamic response, including those whose Doppler and Plethysmographic examinations were within normal limits for noncold exposed individuals, had evidence of vascular compromise at the digital level and benefited from regional sympathectomy with intra-arterial reserpine.