The purpose of the study was to investigate the role of vitamin B6 in the process of melatonin biosynthesis. 30 laboratory white rats were divided into two groups - experimental and control groups. The animals in the first group were treated with vitamin B6 injection. Every other day at 22 00, melatonin concentration was defined by means of ELISA. The experiment has lasted for two months. At the end of the experiment, the plasma level of melatonin increased by 35,95% in the first group of animals in comparison with the second control group. It is found that, B6 vitamin injections strengthens melatonin biosynthesis; consequently strengthening of melatonin biosynthesis influences positive therapeutic effects,; one of the reasons for pathological processes, developed in organism on the background of B6 vitamin deficiency, is reduction of endogen melatonin production.