With the rapid increase in design and installation of ozone facilities in the United States, it has become apparent that there is a need to better define the design basis for the ozone gas and water contacting systems. A systematic approach to the design and operation of ozone contactors for assured disinfection has not been developed by the water industry. Various contacting technologies have been studied and the ozone dissolution characteristics (e.g., transfer efficiency) have been characterized. However this is only half of the information necessary to adequately design and operate a contactor for efficient disinfection and minimization of byproducts. The other half of the information involves understanding the interrelationships among contactor hydrodynamics, ozone residual development, and the spacial and temporal distribution of the ozone within the contactor. To assist in addressing these design and operational concerns, the AWWARF is assisting in funding a study of ozone contacting. The goal of the project is to develop a better understanding of ozone contacting through full scale evaluations to improve contactor design practices and system operations. The study focus is full scale conventional fine bubble contactors and turbine contactors. The project objectives and study results to date are presented.