Context:: Of the approximately 900,000 children who were determined to be victims of abuse or neglect by US child protective services in 2002, the birth-to-3 age group had the highest rate of victimization (1.6%) and children younger than 1 accounted for the largest percentage of victims (9.6%). Objective:: To identify perinatal and sociodemographic risk factors associated with maltreatment of infants up to 1 year of age. Design and Setting:: Observational cohort study. Participants:: 189,055 children born in 1996 in Florida. Main Outcome Measure:: Infant maltreatment, defined as a verified report of abuse, neglect, or threatened harm that occurred between day 3 of life and 1 year. Results:: 1,602 children (.85%) of the 1996 birth cohort had verified instances of maltreatment by age 1. Of 15 perinatal and sociodemographic variables studied, 11 were found to be significantly related to infant maltreatment. Five factors had adjusted relative risks (RR) of two or greater: Mother smoked during pregnancy (RR 2.8); more than two siblings (RR 2.7); Medicaid beneficiary (RR 2.1); unmarried marital status (RR 2.0); low birth weight infant (RR 2.0). Infants who had four of these five risk factors had a maltreatment rate seven times higher than the population average. Conclusions:: Data on nearly all risk factors found to be significantly associated with infant maltreatment are available on the birth certificate. Such information can be incorporated into a population-based risk-assessment tool that could identify subpopulations at highest risk for infant maltreatment. Because resources are limited, these groups should be given priority for enrollment in child abuse prevention programs.