Growth factors may be involved in sudden infant death (SID). Among these factors, the insulin-like growth factor (IGF) family is important in human fetal and perinatal organ growth and development. In order to detect probable differences in the occurrence and distribution of components of the IGF system, tissue samples from liver, lung, skin, parotid and thyroid gland, gut and cerebellum from SID children (n=9) and controls (n=6) aged between 14 and 258 days of life (mean 105 days) were stained immunohistochemically using antibodies against IGF-I, IGF-II and their specific IGF-I-receptor (IGF-IR). In contrast to controls in hepatocytes of SID children a reduction or an absence of immunoreactivity for IGF-I and IGF-IR and a weaker staining for IGF-II was detected. IGF-II in smooth muscle layers in the gut and IGF-I in epithelial cells in intestinal specimens also showed a reduced immunoreactivity in SID children and those who died traumatic deaths. In the other organs examined no significant differences in the distribution of the insulin-like growth factor system between the groups could be detected, indicating that in SID children no fundamental differences or alterations in the physiology of the IGF system occur. Because of the decreased immunostaining of IGFs in the liver and intestine of SID cases, a local dysregulation may be discussed.