During the last 5 years, 640 patients had treatment to their port wine stains (PWS) with a flashlamp-pumped pulsed dye laser. One hundred and fifty-six patients have been discharged for varying reasons, of which 59 (38%) achieved excellent (at least 75%) lightening of their birthmark. Of the remaining patients, those who attended the clinic for the sixth and 12th time for treatment were also assessed to determine the degree of fading achieved in the port wine stain. Our findings confirm that flashlamp-pumped dye laser treatment is safe and effective for the treatment of PWS and that complications are rare. However, the degree of fading achieved is variable and often unpredictable. Fifty-two per cent of facial lesions of different colours achieved over 75% fading as against 18% of non-facial lesions. Sixty-four per cent of those over the age of 50 years had an excellent response whereas only 19% of those below the age of 5 years were able to achieve a similar result. The colour of the port wine stain was found to be of no prognostic value. A search for an accurate and non-invasive method to predict the outcome of flashlamp-pumped pulsed dye laser therapy for PWS is warranted.