To assess the lunar hypothesis as predictive of mental health emergencies and antisocial behavior, the relation of the lunar hypothesis and the occurrence of psychiatric hospital admissions of developmentally disabled adults was examined. The full moon phase of the lunar cycle did not explain a higher rate of hospital admission and accounted for only .007% of the variance. A critique of the methodology in prior research led to the suggestion that more immediate stressors and environmental factors are more plausible contributing factors to hospital admission.