Three hundred sixty-five cases of nontraumatic phakic retinal detachment were examined by analysis of covariance to determine the degree of association among type of detachment, refractive error, and age of onset. The combination of type of detachment and refractive error explained 57% of the variation in age of onset. Discrimination among types of detachment by variation in mean age was limited. Discrimination among types of detachment by variation in mean refractive error could not be established. Detachments due to vitreoretinal adhesion, lattice degeneration, and retinal dialysis differed significantly in mean age of onset and regression of age on refractive error. A regression model was created to predict from refractive error the age of onset with 95% confidence limits for individuals who appear to be at risk for these types of detachment.