The human serotonin transporter (5-HTT) gene is an important candidate for the pathogenesis of mood disorders. Associations have been reported between a variable-number tandem-repeat polymorphism in intron 2 of the serotonin transporter gene (5-HTTVNTR) and mood disorders in a number of studies of Western and Chinese populations. However, no such relationships have been determined in other analogous research. To replicate these positive findings in a Chinese population and to determine the association between onset age of bipolar disorder and 5-HTTVNTR, we investigated the prevalence of this polymorphism in an independent Chinese population (83 bipolar disorder patients, 77 major depressive disorder patients and 169 controls), demonstrating no significant association between the 5-HTTVNTR polymorphism and mood disorders or age at onset. Further, no association was demonstrated between this polymorphism and suicidal history in mood disorder patients. These negative findings suggest that 5-HTTVNTR does not play a major role in the pathogenesis of mood disorder in Chinese populations.