The prevalence of hypopigmented macules among 423 white individuals and their significance in the diagnosis of tuberous sclerosis (TS) were evaluated at the University of Washington School of Medicine and Children’s Hospital, Seattle, WA. Twenty (4.7%) had at least one macule, 4 of these had more than one macule, and none had more than three. Two (8%) of 25 hypopigmented macules were identified only with a Wood lamp. Of the 20 individuals with macules, 13 had ophthalmoscopic exams and none showed retinal changes of tuberous sclerosis. A few hypopigmented macules on the skin of otherwise healthy individuals without a family history of TS do not warrant a search for other signs of the disorder. 
COMMENT. Hypopigmented macules are apparently more common than previously determined, occurring in close to 5% of the general population under 45 years of age. The presence of one to three macules is not by itself a significant risk factor for tuberous sclerosis. As a secondary feature of TS, at least one other manifestation must be present to establish a diagnosis.