Dr. Rashid A. Sunyaev has made a far-reaching influence on contemporary observational cosmology through his theoretical studies of acoustic oscillations in the early universe left their imprint on temperature fluctuations in the cosmic microwave background radiation and the scattering of that radiation by hot electrons in the clusters of galaxies. He has also made significant contributions to high-energy astronomy through his theoretical research on the accretion of matter onto high-density celestial objects and the energy release mechanisms involved, as well as his leadership of international observational projects.