A review contemplates as a whole the problem of regulation of the cellular volume. The first part of the review considers the influences inducing alterations in the cells volume on account of changes in the tonicity of extracellular milieu and cytoplasm. The review elucidates the ways of implementing the fast and slow regulatory volume increase as well as decrease (RVI, RVD). The volume increase seems to enhance cells' proliferative ability due to activation of ions transport. The volume decrease needs further investigations. The last chapter of the review considers pathophysiological significance of the volume regulation in hyponatremia, diabetes, neutrophil activation.