The peroxisome-proliferator-activated receptor gamma2 (PPAR gamma2) is a transcriptional key regulator of adipocyte differentiation. PPAR gamma2 can be inactivated by phosphorylation of a serine residue at position 114. A point mutation leading to an amino acid exchange at position 115 (Pro115Gln) was shown to preclude serine phosphorylation and to consecutively accelerate adipocyte differentiation emphasizing the pathophysiological relevance of this mutation. So far, four markedly obese heterozygote carriers of the Pro115Gln mutation (body mass index 37.9-47.3 kgxm (-2)) have been identified in a circumscribed study population. In order to evaluate the epidemiological relevance of the Pro115Gln mutation in morbid obesity we screened the DNA of all subjects with a body mass index greater than 35 kgxm (-2) who had participated in a nationwide German epidemiological field survey. There was no homozygote or heterozygote carrier of the Pro115Gln polymorphism among them. We conclude that the Pro115Gln polymorphism within the PPAR gamma2 gene has no relevant epidemiological impact on morbid obesity in Germany. It needs further investigation whether this polymorphism might play a role in related metabolic disorders.