The authors examined the association between birth month and longevity for major league baseball players. Players born in the month of November had the greatest longevities whereas those born in June had the shortest life spans. These differences remained after controlling for covariates such as birth year, career length, age at debut, height, and player position. The authors determined that the most likely explanation is that those born during seasons when mortalities are highest are constitutionally weakened and more likely to succumb to life threatening conditions later in life.