One hundred and one patients (112 parts) with port-wine stains were treated by argon laser therapy. We strictly evaluated all patients according to color shift, scar formation, and pigmentation. We observed good to excellent results in 44 percent of patients, and less satisfactory results in 56 percent. The relationship between the effects of treatment and several factors, such as patients' age, anatomic site, and histologic type of the lesions, were investigated. More satisfactory results tended to be obtained in patients with neck lesions and with histologic type III lesions (dilated type). To date we have not discerned any definite criteria for precisely predicting the response of port-wine stains to argon laser therapy. Consequently, the performance of a test seems to us to be the best way of discovering the response and course of healing of an individual port-wine stain after laser therapy. Thirty-six consecutive patients were studied to determine whether compression and cooling would improve the outcome of argon laser therapy. The use of this method did not produce any noticeable effects.