Brain-derived neurotrophic factor (BDNF), a member of the neurotrophin growth factor family, has been implicated in both mood disorders and suicidal behavior. This study has examined the association between the BDNF gene Val66Met polymorphism and mood disorders, age of onset and suicidal behavior in a Chinese sample population. The genotype and allele frequencies for the BDNF gene Val66Met polymorphism did not differ comparing depression groups (total, bipolar disorder or major depression) and control subjects. Furthermore, it was not demonstrated that this BDNF polymorphism was associated with age of onset or suicidal history in our mood disorder patients. Based on these results, it seems reasonable to suggest that this polymorphism is unlikely to play a major role in the genetic susceptibility to mood disorders. Given the fact that the positive association between BDNF gene Val66Met polymorphism and bipolar disorder has only been demonstrated for a Caucasian population but not for a Japanese analog or our Chinese sample, it appears likely that this association is ethnicity dependent.