Using single strand conformational analysis we screened the complete coding sequence of the serotonin 1F (5-HT1F) receptor gene for the presence of DNA sequence variation in a sample of 137 unrelated individuals including 45 schizophrenic patients, 46 bipolar patients, as well as 46 healthy controls. We detected only three rare sequence variants which are characterized by single base pair substitutions, namely a silent T-->A transversion in the third position of codon 261 (encoding isoleucine), a silent C-->T transition in the third position of codon 176 (encoding histidine), and an C-->T transition in position -78 upstream from the start codon. The lack of significant mutations in patients suffering from schizophrenia and bipolar affective disorder indicates that the 5-HT1F receptor is not commonly involved in the etiology of these diseases.