We compared the rate of all-cause mortality in siblings of children diagnosed with fetal alcohol syndrome (FAS) with the siblings of matched controls. The siblings of children with FAS had increased mortality (11.4%) compared with matched controls (2.0%), a 530% increase in mortality. The age of death in case siblings deaths occurred later (between 1 day and 7 years) compared with the controls (1 day to 4 years) [odds ratio (OR)=2.4 (0.4-15.6)]. Siblings of children with FAS had increased risk of death due to infectious illness [OR=13.7 (1.2-361)] and sudden infant death syndrome compared with controls [OR=10.2 (1.2-75.1)]. A diagnosis of FAS is an important risk marker for mortality in the siblings of the proband even if they do not have FAS. Maternal alcoholism appears to be a useful risk marker for increased mortality risk in diagnosed cases and their siblings. This has important implications in the management of family members of children with FAS.