Data were obtained on 171 individuals with Sturge-Weber syndrome via questionnaire and medical records. The age of the study group ranged from 2 months to 59 years; the median was 8 years. In addition to the facial location of port-wine stains in the areas of the trigeminal dermatomes present in 170 patients, 45% also had extracranial port-wine stains over the torso and/or extremities, and 17% had other vascular or pigmentary lesions. Seizures were present in 80% of all patients (87% of those with bilateral and 71% of those with unilateral port-wine stains); in all but one case, seizures were associated with port-wine stains in V1 alone or V1 and V2 trigeminal dermatomes location. The age of onset of seizures ranged from birth to 23 years; 75% had onset of seizures before 1 year of age; these children had an 83% incidence of developmental and academic problems. Fifty-eight percent showed early developmental delay and required special education classes. The rate of retardation showed a decreasing tendency with increasing age of onset of seizures; of the children without seizures, only 6% had developmental delay and 11% required special education classes. Glaucoma was present in 48% of patients (67% unilateral and 33% bilateral). Of all patients with glaucoma, 92% had port-wine stains in both V1 and V2 dermatomes and 8% only in V1. The laterality of glaucoma did not correspond to the trigeminal distribution of the port-wine stains in all instances. Glaucoma was diagnosed during the 1st year of life in 61% and by 5 years in 72%; one patient did not have onset of symptoms until 38 years. The results of our data can serve as a guide for estimating relative risk figures for seizures, glaucoma, and mental retardation in children with Sturge-Weber syndrome.