Homicide is the 15th leading cause of death during the first year of life (i.e., infancy) in the United States. In addition, the risk for homicide is greater in infancy than in any other year of childhood before age 17 years and is greatest during the first 4 months of life. To determine how the risk for homicide varied by week during infancy and by day during the first week of life, CDC analyzed death certificate data for 1989-1998. This report summarizes the results of this analysis, which indicated that risk for infant homicide is greatest on the day of birth. Efforts to prevent infant homicides should focus on early infancy.