Results from an analysis of 287 patients in 20 series do not support widely held concepts of the descriptive epidemiology of Mooren's corneal ulcer, i.e., that bilateral disease is more common in younger patients and blacks. Our review shows that the disease is reported 1.6 times more frequently in males than in females regardless of race or age. Black patients are five times more likely to be young than are white patients. However these figures may be misleading since they are not calculated from population-based estimates. Our analysis highlights misconceptions and emphasizes the hazards of drawing conclusions about the epidemiologic characteristics of this disease based on currently available data.