The serotonin (5HT) receptor genes are considered good candidates for Major Depression (MD), Bipolar Disorder (BP), and Obsessive-Compulsive Disorder (OCD). The 5HT1Dbeta receptor gene has at least three polymorphisms known: G861C, T-261G, and the functional T371G (Phe-124-Cys). The aim of this study was to investigate for the presence of linkage disequilibrium between the 5HT1Dbeta receptor gene and BP. Two hundred and ninety probands with DSM-IV BPI, BPII, or Schizoaffective Disorder (Bipolar type) with their living parents were recruited. Genotyping data for the G861C and T371G polymorphisms were analyzed using the Transmission Disequilibrium Test (TDT). One hundred and sixty triads were informative for the TDT on the G861C polymorphism, which showed no preferential transmission of either allele (chi-square = 0.438, df = 1, p =.508). Only four triads were suitable for the analysis on the T371G variant, with the T allele transmitted once and the G allele transmitted four times to the affected. These findings validate further the results of pharmacological studies excluding a direct involvement of the 5HT1Dbeta receptor in the pathogenesis of BP. Further investigations combining genetic and pharmacological strategies are warranted.