Cooling tower operators are currently confronted with a variety of contemporary chemical treatment and chemical/physical control processes as vendors of chemicals and equipment attempt to fill the vacuum created by the regulatory restriction of chromate based programs from our industrial arsenal.  A number of apparently conflicting claims currently exist regarding the cycles of concentration that can be effectively maintained in open recirculating cooling water systems using various alternative control/treatment schemes with and without pretreatment.  Users have suffered poor results by following vendor recommendations.  In this paper the author discusses many of the common control/treatment schemes and provides both a theoretical basis for each program and practical guidelines on their performance and imitations.