The paper surveys controllability in the stress theory. Uncontrollable action is perceived by living organisms in a principally different way than the controllable one and induces persisting pathological changes. The controllability, i.e. presence of a feedback in the stimulus/response system, is determined by an interaction of the medium factors and a strategy of subject's behaviour. A passive strategy proves to be optimal for adaptation under the conditions when an animal cannot change unfavourable medium conditions. The authors base their theoretical statements on their own experimental studies as well as literature references analysis.