This work reports on a study of the uptake of cadmium and zinc, both singly and in combination (in equimolar concentrations), by the yeast Saccharomyces cerevisiae. It is shown that in all cases, an instantaneous surface adsorption occurred, followed by a slower uptake process. lit the dual metal ion system, the presence of the co-ion did not appreciably affect the instantaneous uptake of the other metal, suggesting that the two metal ions may be bound to different sites on the cell. The long-term uptake was however metal-dependent; inhibition in the uptake of zinc by cadmium was observed, but zinc had no effect on the long-term uptake of cadmium. Non-interaction and antagonism were demonstrated in the uptake of cadmium and zinc respectively by Saccharomyces cerevisiae. Treatment of the yeast cells with heat, acid alkali or formaldehyde was found to enhance the instantaneous specific uptake. Formaldehyde-treated cells consistently showed significantly greater uptake than non-treated cells.