Introduction. In the modern world people are exposed to the influence of adverse psychological and physical factors, escalating in intensity. The search for new pharmacodynamic effects of [1,3,5]-thiadiazine derivatives designated by significant biological activity of these compounds is an essential issue.Aim. To research adaptogenic activity of tetrahydropyrido[2,1-b][1,3,5]thiadiazine derivatives using a modified Porsolt Forced Swim Test.Materials and methods. Four substances from the group of 3-R-8-aryl-6-oxo-3,4,7,8-tetrahydro-2H,6Hpyrido[2,1-b][1,3,5]thiadiazine-9-carbonitriles were selected for the research. Rats were divided into a control group, 5 reference groups (amitriptyline, caffeine, thiotriazolin, thiocetam, ginseng) and 4 experimental groups according to the number of the studied original tetrahydropyrido[2,1-b][1,3,5] thiadiazine derivatives.Results. Intragastric injection of substance 2 for 5 days in the modified forced swim test (forced swimming with freight) increased work capacity and endurance of the rats by 103.42% as opposed to the initial results. The detected adaptogenic activity of this tetrahydropyrido[2,1-b][1,3,5]thiadiazine derivative six times exceeds adaptogenic activity of ginseng and seven times that of amitriptyline. The rats in the control group were active for a bit longer time. Ginseng raised the time of activity by 17% at day 5. Caffeine essentially reduced work capacity and endurance. Amitriptyline showed adaptogenic activity at day 3 of the research (increase by 10.4%). Thiotriazolin also showed adaptogenic activity on day 3 of the research (increase by 30.17%). Thiocetam increased the time of activity by 78.55%. Substance 4 had adaptogenic activity too; it increased the time of activity in aversive conditions by 58.25%, which three times exceeds this parameter for ginseng and four times for amitriptyline.