An epidemiological analysis of 38 cases of SIDS was carried out in the Pathology Institute of the University of Milan. Those cases were collected from Milan district in four years, from 1987 to 1991. In 1991 the incidence of cot death in the same district was 0.55 per 1000 live births. This study has led to the following conclusions. Most of SIDS victims were males, mostly aged between 40 and 90 days; the totality (except one case that happened during maternal feeding) of the cases occurred during night sleep; a greater prevalence during winter months was found. We didn't find any correlation between type of feeding and cot death. The weight at birth was mostly satisfactory; often the infants showed mild infections of the upper airways during the days immediately before death. It is possible to hypothesize a correlation between cigarette smoking and between drug abuse (during pregnancy) and cot death. We didn't recognize a significant association between sleeping position of infants and their death nor between type of cushion and cot death. For each case a complete autopsy was carried out. We extended histological findings to cardiac conduction system, to brain-stem (central) and to ganglion structures (peripheric), sites of cardio-respiratory control. In 65.7% of cases we found cardiac conduction system alterations; in 10.5% of cases we observed brain-stem anomalies, sometime these alterations were associated. In one case we noticed an hypertrophy of aorto-pulmonary paraganglia structures.