Additional illumination of animals nonselected for domesticative behaviour, results in the earlier increase of estradiol level in the blood and in higher production of this hormone by the gonads during pubertal period. Artificial illumination regimes do not significantly affect estradiol-producing activity of the ovaries in animals selected for domesticated behaviour. At the same time, additional illumination of the females with this type of behaviour increased progesteron-producing function of the adrenals during sexual maturation. Thus, selection of silver foxes for the domesticated type of behaviour affects the sensitivity of hormonal function of the ovaries and adrenals to photoperiodic factor of the environment.