A detailed characteristic of casein kinases of the second type based on the analysis of the literary data and own research is given. The main properties which allow to differ them from other protein kinases are described. The participation of casein kinases II in regulation of different cellular processes are shown: in carbohydrate and lipid metabolism, in transcription, translation and enzyme synthesis. The changes in the activity of the given casein kinases in the course of the cellular cycle and during some pathological states show that from the diagnostic point of view the measurements of the enzyme activity is a useful tool, especially in an early detection of uncontrolled cell proliferation. On the basis of the given data the casein kinases II have been concluded to play an important role in the control of organism normal development. The given proteins may be put in one line with well studied and physiologically important cAMP-dependent and Ca-dependent protein kinases.