This retrospective review of the records of the North Carolina Office of the Chief Medical Examiner focused on all infants ages 0-1 year old who died suddenly and unexpectedly during 1999 and 2000. Infants whose deaths were attributed to accidental asphyxia or aspiration were included in the study due to the possibility of a diagnostic overlap with SIDS. Infants with a documented history of natural disease that caused the death were excluded, as were deaths due to motor vehicle accidents or other trauma. The study was further limited to infant deaths in which the sleep surface, sleep position, and occurrence of co-sleeping were known. The study population included 102 infant deaths, with 75 of these being younger than 4 months. Of the 102 SIDS deaths, 67 (65.7 percent) were not in a crib, 63 (61.8 percent) were prone when they died, and 48 (47.1 percent) were co-sleeping. Ninety-four of the deaths had at least 1 risk factor present. Only eight (7.8 percent) infants had slept alone, in a crib or bassinet, and on their back or side. Infants less than 4 months old had a higher rate of co-sleeping (54.7 percent) than the older infants (25.9 percent), as well as a higher frequency of heart malformations diagnosed at postmortem examination. The older infants were more likely to exhibit pulmonary and tracheal inflammation and neuropathology. 1 table, 3 figures, and 12 references