A retrospective analysis was carried out of 150 SIDS cases seen in the five year period between 1979 and 1983 in Hamburg, Germany. The overall incidence was 2.3 per 1,000 live births. 82% of all infants and 100% of the preterm infants (corrected according to gestational age) dying of SIDS, died within the first 6 months of life. Infants of mothers less than 18 years of age, infants with more than 2 siblings, infants with birthweight less than 1,500 g and SGA-preterm infants were found to be high-risk subgroups. A high percentage (20% of all cases, 43% of infants with mothers less than 18 years) were underweight at death (under the 3rd weight-percentile). The study emphasizes the complexity of internal and external factors in the etiology of SIDS.