The role of serotonin transporter (SERT) protein in the development of somatoform disorders (SD) was investigated. An association study was performed in terms of the evaluation of the level of SERT immunoreactive (IR-SERT) protein using site-specific antibodies directed at SERT C-terminus fragment, poorly conserved among the other cotransporters. The level of the anxious symptomatology was also estimated in the patients with SD. 22 patients, who met DSM-IV criteria for somatoform disorders, and 32 normals were examined. In platelets from normals, IR-SERT protein migrated as a difuse band between 68 and 105 kDa, and a major sharper band at 43 kDa. Almost complete disappearance of platelet 43 kDa IR-SERT protein band was observed in most of the patients with SD. These findings permitted to suggest a possibility of either biosynthetic or processing abnormality of SERTs in the affected population, that might reflect a dysfunction of serotonin neurotransmission in CNS of the patients with SD.