1. The impulse ultrasonic method of determining the strength of concrete in a tunnel lining can be considered acceptable in practice and fully reliable. 2. The quality of the concrete of the Inguri diversion tunnel lining is satisfactory with the exception of a few spots and meets the design requirements. 3. The method employed for determining the quality of concrete of the diversion tunnel lining of the Inguri hydroelectric scheme can be widely used for estimating the strength of concrete of tunnel linings, and in other places, including for the entire diversion tunnel.