All patients with port wine stains (PWS) attending a tunable dye laser clinic were examined by one author (SWL), forming a large group which has allowed study of the demographic data of such patients. Two hundred and eighty-three patients, 217 females (median age 24 years, range 0.5-73) and 66 males (median age 20 years, range 0.75-72), were examined. The PWS were on the face in 226, neck in 69, trunk in 36, upper limb in 35 and lower limb in 29. The commonest lesional colour was purple (63 patients), while 39 naevi were pink/red, 35 pink/ purple and 35 pink. The naevus was flat in 255 patients, cobblestoned in 28, associated with hypertrophy in 31 and with scarring in 22. Seventy-two patients (25.4%) had a positive family history of birthmarks, 20 strawberry haemangiomas and 22 PWS, the family history of PWS being higher than expected for the prevalence of this naevus in the population. One hundred and forty-six patients were also examined for naevus anaemicus which was noted in 12 (8.2%), confirming an association between these two naevi. Ninety-four patients had received previous treatment, most commonly with the argon laser (56 patients), of whom only five reported a good result, and 17 of 22 patients with treatment-related scarring had been treated with this laser. Cosmetic camouflage was used in 109 (38.5%) of patients, who usually had PWS on the face (94%), of whom only 46 (16%) had received advice of its use.