The purpose of this study was to determine the relative importance of inadequate gestational weight gain as a cause of infant mortality. Birth and infant death certificate data were obtained from a random sample of 100,000 records from the National Center for Health Statistics (NCHS) 2002 Birth Cohort Linked Birth/Infant Death Data File. Descriptive and proportional hazards regression analyses were used to assess the odds of infant mortality associated with inadequate gestational weight gain compared to normal weight gain. Nearly 30% of women experienced inadequate weight gain. Infants born to women with inadequate gestational weight gain had odds of infant death that were 2.23 times the odds for infants born to women with normal weight gain. Increased odds remained after adjustment for gestational age, low birth weight, maternal age, maternal education, and maternal race. Among racial or ethnic subgroups, African American women were 1.3 times as likely as white women to have an infant die, but they were no more likely to have an infant die than white women if they had inadequate weight gain. There is a substantial and significant association between inadequate gestational weight gain and infant death that does not differ by race, ethnic group membership, or maternal age.