INTRODUCTION: The role of pulsed dye lasers (PDL) in the treatment of childhood haemangiomas is controversial. Our aim was to compare treatment with PDL with a wait-and-see policy. METHODS: We did a prospective, randomised controlled trial in which we enrolled 121 infants aged 1-14 weeks with early haemangiomas. We assigned infants to PDL treatment (n=60) or observation (n=61), and followed them up to age 1 year. The main outcome measures assessed were proportion of lesions completely clear or with minimum residual signs, adverse reactions, including pigmentary disturbance and skin atrophy, complications such as ulceration and infection, proportion of children whose parents considered the haemangioma a problem, characteristics of the haemangioma, and an independent assessment of the haemangioma problem by a panel of five parents. Analysis was by intention to treat. FINDINGS: All infants completed the study. The number of children whose lesions showed complete clearance or minimum residual signs at 1 year was not significantly different in the PDL treated and observation groups (25, 42%, vs 27, 44%; p=0.92). However, PDL treated infants were more likely to have skin atrophy (17, 28%, vs 5, 8%; p=0.008) and hypopigmentation (27, 45%, vs 9, 15%; p=0.001). The frequency of complications was similar between groups. The only objective measure of resolution that improved with PDL treatment was haemangioma redness. The number of children whose parents considered the haemangioma to be a problem at 1 year did not differ much between groups (11 of 60, 18%, vs 9 of 61, 15%; p=0.78). The independent parent panel validated this result. INTERPRETATION: PDL treatment in uncomplicated haemangiomas is no better than a wait-and-see policy.