Experimental and theoretical research on neutral excitations in a two-dimensional electron gas in a high magnetic field is reviewed. Methods for calculating excitation energies in the high field limit for integer and noninteger filling factors are considered. The effects of impurities and of the nonideality of the two-dimensional system on the excitation spectrum are examined. Experimental results that have been obtained by the method of nonelastic light scattering and lend support to the current theoretical views are presented. The review discusses with possible directions for future experimental and theoretical work.