We have investigated the role of Ag in the AgyMn1-x-yCdxS during photocatalytic H-2 evolution under visible light irradiation (lambda > 420 nm). The rate of H-2 evolution increased with the amount of Ag doping, and reached a maximum at y = 0.003 (x = 0.40). AgyMn1-x-yCdxS consisted of a highly crystalline solid solution phase over the range 0.48 <= x <= 0.63 and 0 <= y <= 0.02, suggesting that the effect of Ag on the photocatalytic activity is not associated with crystallinity. UV-vis absorption spectra of AgyMn1-x-yCdxS showed a band gap absorption at 500 nm and a flat absorption above 500 nm. The latter absorption was caused by the presence of Ag2S, which does not significantly contribute to the photocatalytic activity. X-ray photoelectron spectroscopy detected metallic Ag on the surface of Ag0.003Mn0.40Cd0.60S, which could act as a co-catalyst in photocatalytic hydrogen evolution. (C) 2012 Elsevier B.V. All rights reserved.