Gender differences in the prevalence of affective disorders were suggested by several authorities in the field. Such differences may be attributed to sex-related differences in levels or activity of monoamine transmitters, especially since some of these variables have been shown to be altered by gonadal hormones. The reported association of perimenstrual and postpartum dysphoria, with affective disorders may contribute to further elucidation of pathophysiology of depression in women--in light of the hormonal-behavioral dynamics of these periods. Several factors associated with monoamines biosynthesis, availability, uptake and metabolism were found to be more abnormal in normal and depressed women compared to men. Age-sex differences in some biological markers for depression are reported as well. Their relevance to the underlying pathophysiology of depression is unclear but they may provide clues for further research.