CdS catalysts, prepared using difference precursors, were characterized and tested for the photocatalytic reduction of nitrite to ammonia using sodium sulphate and sodium sulphite as sacrificial agents. The catalyst prepared from cadmium nitrate and sodium sulphide and treated at 623 K showed maximum activity. The activity was enhanced by loading with noble metals, such as Ru, Pd or Ir, or by the use of hole transferring agents, such as RuO2. The photoefficiency for the photocatalytic reduction of nitrite to ammonia was found to be 2.6%. © 1995.