Genetic factors are of importance for the development of the metabolic syndrome and type 2 diabetes, but despite extensive research the identification of the underlying genes has not been fruitful. This report focuses on the interactions between intrauterine growth and genes in relation to adult health outcomes based upon findings from the Helsinki Birth Cohort Study. Candidate genes for type 2 diabetes and the metabolic syndrome have been focused upon and we report on interactions between polymorphisms of the peroxisome proliferator-activated receptor (PPAR)gamma-2, plasma cell glycoprotein (PC-1) and the glucocorticoid receptor (GR) genes and - prenatal growth in relation to adult health outcomes. In elderly individuals the effects of the Pro12Pro/Pro12Ala polymorphisms of the PPARgamma-2 gene depend on their body size at birth. Individuals, who had a small body size at birth and were carriers of the Ala allele, seem to be protected against insulin resistance and type 2 diabetes in later life. Similar gene environment interactions will be described in relation to the PC-1 and the GR genes. We propose that these findings reflect gene-early environment interactions and can be attributed to the phenomenon of developmental plasticity.