In Wisconsin, the rate of postneonatal deaths attributed to sudden infant death syndrome (SIDS) for the period 1978-1987 was 6.7 per 1,000 live births for Native Americans, 3.6 for blacks, and 1.4 for whites. To investigate racial differences in case ascertainment and risk for SIDS mortality, this study used matched birth-death certificate data for the 1,111 reported SIDS deaths during the 10-year period. At least 90% of all SIDS deaths occurred before 6 months of age; seasonal variation in time of death and autopsy rates were similar by race. The reported higher risk of SIDS for male infants and those with low birth weights did not occur among Native Americans. Low birth weight was a stronger risk for SIDS among whites than blacks. Our findings suggest that diagnostic practices may not account for racial differences in SIDS mortality. Patterns of risk, however, appear to vary by race.