This paper presents the preliminary results of an ongoing research project designed to document the identity and concentrations of atrazine degradation products in raw and treated drinking water supplies, to examine the ability of various water-treatment processes (including ozonation and GAC adsorption) to remove atrazine and its degradation products from drinking water, and to determine the extent to which additional atrazine degradation products are formed during treatment. The results of two separate studies are presented: (1) a pilot-plant study designed to examine the removal of atrazine by ozone and GAC, as well as the formation of volatile atrazine degradation products by ozone and their subsequent removal by GAC; and (2) a laboratory study designed to examine the effects of pH, ozone concentration, and contact time on the removal of atrazine and the formation of both volatile and nonvolatile ozone-derived atrazine degradation products.