: Numerous studies have provided information indicating the involvement of oxidative stress in the pathophysiology of depressive disorder (DD). The antioxidative system protects against the effects caused by reactive oxygen species (ROS). Catalase (CAT) is one of antioxidative enzymes observed to change their levels in the course of depression. The enzyme decomposes hydrogen peroxide (H(2)O(2)), whose overproduction is a result of many processes taking place in depression. Therefore, functional polymorphism of the CAT gene can be a candidate marker of the risk of depression. The presented study assessed the correlation between -262C>T polymorphism of the CAT gene, which influences the increase of CAT expression and activity, and the risk of depression development. The study, carried out on a homogeneous group recruited from the Polish population, enrolled 149 healthy subjects and 149 depressive patients. The groups were age-matched. The obtained results indicate no correlation between -262C>T polymorphism of the CAT gene (both with respect to genotype distribution and allele frequency) and the risk of depression. Nevertheless, further studies assessing the correlations between depression and polymorphism of the genes encoding antioxidative enzymes on larger groups of subjects should be undertaken.