Total butyrylcholinesterase activity (EC 3.1.1.8) was previously suggested as a marker for metabolic syndrome. The present study examined total butyrylcholinesterase activity and the relative and absolute activities of two butyrylcholinesterase electrophoretic bands (C(4/5) and C(OF) in 99 obese individuals (body mass index > or = 30 kg/m2) presenting the CHE2 C5- phenotype of the CHE2 gene. Anthropometric, hormonal and biochemical variables already associated with metabolic syndrome were also examined. The data from these obese individuals of the CHE2 C5- phenotype show that total butyrylcholinesterase activity and the absolute activities of the C(4/5) and C(OF) electrophoretic bands are associated with metabolic syndrome and with variables related to it. These butyrylcholinesterase activities do not behave as independent risk factors for metabolic syndrome, but can be considered as secondary markers for this syndrome in obese individuals with the CHE2 C5- phenotype.