Abstract: This article reviews the methods of studying the nuclear structure by means of the nuclear reaction as a tool for investigation. It is divided into two parts. The first part is mainly concerned with the properties of the individual low-lying levels of nuclei, a brief outline being given to describe the present situation of cumulation of experimental results and the current theories developed to account for them. The second part reviews the experimental methods tried for studying the virtual states of nuclei. In both parts, typical types of nuclear reactions used in these investigations are described.