Uncertainty is inherent in the modern world. Global problems of the present, environmental,
cultural and social problems, information revolution, problems of interpersonal communications
and interaction of the person with the environment, all this generates uncertainty of human's
existence of the person in the world. Under such circumstances of the existence a special role is
played by a tolerance phenomenon to uncertainty. In this regard, in spite of sufficient complexity
and relevance of a phenomenon of tolerance to uncertainty and interest in this problem of various
sciences, there are no theoretical and empirical data on features of tolerance to uncertainty and
the tested mental states of various ethnocultural groups, in particular of Russians and Tatars, that
defined the purpose of our research. The research was conducted by means of a technique of a selfassessment of mental states of Alishev, Gabdulkhakova. In article are presented and analized the
results of a research of mental conditions of representatives of the Russian and Tatar nationality
in situations with a certain and uncertain outcome. It is revealed that at collision with uncertain
situations there is a shift of qualitative characteristics of states from positive to negative at examinees
of the Russian and Tatar nationality. It is shown that in situations with defined (negative outcome
there are negative mental states, while in situations with a certain outcome positive states are felt.