The 1,4-cyclohexanedione/hydroquinone/BrO3/ferroin reaction system is uncovered to exhibit photo-controlled oscillatory reaction dynamics, in which illuminations with visible light can either induce or inhibit chemical oscillations. The observed behavior exhibits strong dependence on the wavelength of the incident light and the initial concentrations of hydroquinone and the metal catalyst ferroin. A possible photo-reaction path is suggested on the basis of experimental observations. (C) 2003 Elsevier B.V. All rights reserved.