There exists a popular belief in the causal relationship between the moon's phase and the incidence of major trauma. In this retrospective study we reviewed 1,444 trauma victims admitted to the hospital during one calendar year. Full moons were defined as three-day periods in the 29.531-day lunar cycle, with the middle day being described in the world almanac as the full moon. Victims of violence included those patients sustaining blunt assault, gunshot wounds, and stabbings. There was no statistical difference in number of trauma admissions between the full moon, 129 patients per 36 days (mean, 3.58), and nonfull moon days, 1,315 patients per 330 days (mean, 3.98). Mortality rate, 5.4% versus 10.3%; mean Injury Severity Score, 13 versus 15; and mean length of stay, ten versus 12 days, were not significantly different during the full moon and nonfull moon days. Victims of violence were admitted at a similar frequency on full moon, 16 patients per 36 days (mean, 0.444), and nonfull moon days, 183 patients per 330 days (mean, 0.555). We conclude that the belief in the deleterious effects of the full moon on major trauma is statistically unfounded.