A mechanism for initiation effects is proposed. This is based on the theory of non-specific response of cells to damaging influences, which has been developed by the author previously. The effects (adaptive response, stimulation of proliferation, etc.) are believed to be initiated by disturbance of the functions of plasmatic and intracellular membranes which decreases the concentration of low-molecular cellular metabolites and affects their compartmentation. The presence of a lower threshold of the effects, the maximum in the dose dependence as well as dose rate and dose value effects in the range of low doses are explained.