Hypertrophic scars are common and cause functional and psychologic morbidity. The conventional pulsed dye laser (585 nm) has been shown previously to be effective in the treatment of a variety of traumatic and surgical scars, with improvement in scar texture, color, and pliability, with minimal side effects. This prospective study was performed to determine the effectiveness of the long-pulsed dye laser (595 nm) with cryogen-spray cooling device in the treatment of hypertrophic scars. Fifteen Asian patients with 22 hypertrophic scars were treated by the long-pulsed dye laser (595 nm) with cryogen-spray cooling device. In 5 patients, the scar area was divided into halves, one half of which was treated with the laser, whereas the other half was not treated and was used as a negative control. All patients received 2 treatments at 4-week intervals, and evaluations were done by photographic and clinical assessment and histologic evaluation before the treatment and 1 month after the last laser treatment. Treatment outcome was graded by a blind observer using the Vancouver General Hospital (VGH) Burn Scar Assessment Scale. Symptoms such as pain, pruritus, and burning of the scar improved significantly. VGH scores improved in all treated sites, and there was a significant difference between the baseline and posttreatment scores, corresponding to an improvement of 51.4 +/- 14.7% (P < 0.01). Compared with the baseline, the mean percentage of scar flattening and erythema elimination was 40.7 +/- 20.7 and 65.3 +/- 25.5%, respectively (P < 0.01). The long-pulsed dye laser (595-nm) equipped with cryogen spray cooling device is an effective treatment of hypertrophic scars and can improve scar pliability and texture and decrease scar erythema and associated symptoms.