Background: The excimer laser can deliver high-intensity ultraviolet B (UVB) energy at 308 nm, a wavelength similar to that used in narrow-band UVB phototherapy. Objective: The goal of this investigation was to evaluate the role of high-dose single treatments with the excimer 308-nm laser in stable plaque-type psoriasis. Methods: Eighteen volunteers were enrolled in the study. Two plaques were selected and half of each plaque was held as a control while the other half was treated with a single dose of either 8 or 16 times the minimal erythema dose. Results: Sixteen subjects completed the study. Two patients signed up but never actually participated because of scheduling problems. Eleven showed significant improvement within 1 month, and 5 still demonstrated persistent areas of clearing at 4 months. Conclusion: As little as one high-dose excimer laser treatment can be effective for localized plaque-type psoriasis. Multiple treatments or other irradiation schedules with this innovative device may prove even more efficacious. (J Am Acad Dermatol 2002;46:732-7.)