The presented paper concerns the problem of adaptation and its relations to diseases and compensation. Adaptation is a quality of the healthy life and belongs in this manner to the kinds of epigenetic regulation. Disease and adaptation are strongly to distinguish. In relation to the disease the ability of adaptation is in so far of importance as a disease develops in the case of a diminished adaptation. The individual different adaptability is responsible for the different effects of pathogenic factors. Adaptation and compensation represent different qualities. A definition of adaptation is proposed.