Two solution studies were conducted a) to investigate the uptake of zinc (Zn) and cadmium (Cd) by rice plants (Oryza sativa L.) and interaction between these elements, and b) to determine experimental conditions for growing rice grain with desired Cd concentration for an animal feeding study. In both studies, free metal activities of cadmium and cationic microelements were buffered by an excess of chelating agents. The first study was a factorial design with two Zn levels (1.0 and 3.89 mM) and four Cd levels (0.81, 1.44, 2.56 and 4.55 mM) in the solution. In the second study, rice was grown in two solutions of different microand macro-element compositions and three Cd levels (0.0, 0.5, and 2.0 mM). In the first study, solution Zn concentration of 3.89 mM and corresponding free metal activity (pZn 2þ ) of 6.00 was toxic to young rice plants. With time, Zn concentrations in rice plants decreased while Cd concentrations increased. Toxic concentration of Cd in roots (about 100 mg kg À1 ) associated with