Thirty-three cutaneous capillary and mixed hemangiomas in 24 patients were treated prospectively with the flashlamp-pumped pulsed dye laser. Patients ranged in age from 2 weeks to 7 months; the follow-up period was up to 22 months. Some patients received therapy until the lesion was almost clear or until the lesion failed to respond; others received treatment only until active capillary lesional proliferation abated. In the first group of patients, 18 of 25 lesions that were 3 mm or less in elevation lightened with therapy (93.9% +/- 4.6% in 4.1 +/- 1.6 treatment sessions) and flattened to 0.3 +/- 0.4 mm in thickness. The seven lesions that were 4 mm or more in thickness lightened 85.7% +/- 7.3% in 7.0 +/- 2.0 treatment sessions but showed less diminution in thickness (to 3.4 +/- 3.6 mm; p less than 0.01). The second group of patients, who received therapy until proliferation ceased, required just one to three therapeutic sessions. Three of the four lesions that showed residual atrophy were 4 mm or greater in thickness; the fourth lesion was ulcerated on presentation. None of the lesions had residual induration or scarring. We conclude that the flashlamp-pumped pulsed dye laser may successfully prevent enlargement and promote involution of capillary hemangiomas with minimal adverse effects. Therapy is most appropriate for patients with hemangiomas at sites of potential functional impairment, of maceration or ulceration, and of significant cosmetic disfigurement. Therapy should be initiated as early as possible, when lesions are relatively flat, for optimal results.