To determine whether preterminal hyperthermia is significantly associated with sudden infant death (SID), 140 structured interviews with parents of SID victims were compared with questionnaires filled in by a control group of parents living in the same area. All SID autopsies were performed between 1986 and 1992 at the Institute of Legal Medicine of Hannover Medical School according to the same protocol. Signs of profuse sweating (i.e. moist head, damp clothing or bedding) were present at the scene of death in 35.7% of cases. SID victims with signs of profuse sweating were more frequently found under their bedding (p < 0.001), were older (178 vs. 130 days) and the time period between when they were last seen alive and when they were found dead was longer (6.5 vs. 4.5 hours p < 0.01) compared to cases without sweating. Sweat on the head [odds ratio (OR) = 1.9; 95% confidence interval (CI) = 1.0, 3.6], and sweaty clothing and bedding (OR = 17.9; 95% CI = 8.7; 37.1) showed a significant association with the risk for SID. The pathophysiological basis for hyperthermia is SID remains to be determined. Hyperthermia could result from infection, overinsulation from excessive clothing with high environmental temperatures, covering of the infant's head or immature central thermoregulatory centres. The influence on the fatal outcome and the role in the pathogenesis of these deaths requires further research.