The ion exchange behavior and hydrolysis rate of the detergent builder Type A zeolite have been studied in a variety of artificial and natural surface water samples. The experiments were conducted at zeolite A and trace metal concentrations characteristic of what could occur in receiving waters. The data indicate that Type A zeolite hydrolyzed extensively in the test waters at rates which were strongly dependent on hydrogen ion concentration. Half lives of 1–2 months were typical for waters at a neutral pH. Also, the extent of trace metal ion exchange was low (< 10%) for the metals Cd, Cu, Ni and Zn. Pb exchange was slightly higher. It is concluded that the use of the zeolite in detergents will result in little effect on the trace metal distribution of surface waters owing to the low degree of ion-exchange by the zeolite and its hydrolysis products.