To investigate a potential relationship between an elevated lead burden and sudden infant death (SID), the lead concentrations (Pb-B) were determined in 41 blood samples from SID babies and compared with the Pb-B of 5 babies who died traumatically and 77 living control babies. Several factors that may influence the Pb-B were taken into consideration, especially a dependence of the Pb-B on age and social class. Moreover, a post-mortem water shift occurs in the blood. Even taking these factors into consideration the distribution of the Pb-B's of the SID group was found to differ on a highly significant level (greater than 99.9%) from the control group. Five Pb-B's of the SID group were higher than the highest lead concentration found in blood from the control babies. Negative influences of lead on the pre- and postnatal maturation of the brain are discussed in the search for a possible causal connection between an elevated lead burden and the occurrence of SID.