Seasonal variations in the content of dopamine (DA), norepinephrine (NE) and homovanilic acid (HVA) in the forebrain and midbrain were studied in 258 male Wistar rats. The experiments were carried out monthly for a period of 6 years. The content of DA, NE and HVA varied significantly during the year, the changes in the both parts of the brain being unidirectional. The content of DA during winter and spring months was higher, while during summer it was lower than the mean annual value. The content of NA during spring months was significantly higher (by one third in the midbrain) as compared to the mean annual value. Dopamine metabolism was accelerated (DA decrease and HVA increase) in the summer months June, July, August, with the content of NA reaching the mean value.