The behavior of individuals and their responses to external stimuli are controlled by the microsocial environment, which for most mammals is associated with dominant-subordinate relationships. Physiological and behavioral differences between dominant and subordinate individuals may be 'primary' (genetically determined) or 'secondary' (due to position in the group's hierarchical structure). A series of experiments was conducted to investigate the physiological (pain response threshold), immunological (thymus, spleen weights, primary immune response), and behavioral (motor activity, behavior in a shuttle box test) characteristics of dominant and subordinate individuals in groups of three laboratory mice formed on the basis of linear hierarchy. Assessment of the effects of group conditions was made using a conditioned reflex location preference test. The results showed: 1) there are no statistically significant differences in physiological and behavioral (except for motor activity) parameters between dominant and subordinate mice; 2) co-housing of dominant and subordinate individuals in groups with stable hierarchical relationships was not aversive for them.KEY WORDS: Mice, dominance, subordinacy, stress, aggression, locomotor activity.Mouse-like rodents have territorial-hierarchical social structure [6] and in natural conditions dominant individuals expel subordinate individuals from their territory [16]. In laboratory conditions, where males are kept in a shared cage, despotic or strict dominance can be seen [15], where one male dominates and the others are subordinate. Some males of such a group can also show aggression, which is seen after removal of the most aggressive male (the ct male) [9]. Apart from high levels of aggression, the dominant animals is also characterized by behavioral features such as patrolling the territory and aggregating subordinate individuals [9], dominance with regard to access to water and food in conditions of deprivation [16], shorter latent periods tor first attacks on outlanders entering the patrolled territory, and higher frequencies and longer mean durations of attacks [2]. The tormation of 1Department of Psychopharmacology, A. V. Val'dman Institute of Pharmacology, Academician I. P. Pavlov St.