The paper reviews the factors defining excessive growth of the information in medicine. The specific peculiarities of medical data are investigated; the essence of Big Data phenomenon and its potential in electronic medicine are defined. Big Data applications are systematized, and their capacity for the support of medical and diagnostic and management decisions is shown. Advantages of Big Data-analytics in this sphere are indicated in the context of development and transformation of medicine. The challenges, limiting the usage of Big Data in medicine, and the standpoint directions of its application in the given subject field are specified (pp.8-24).