Refinery managers and operators have known that cyanide is present in petroleum refinery effluent for a number years.1,2 Cyanide levels in refinery effluent are usually much lower than those in wastewater from metal finishing and plating industries, however, and cyanide control in petroleum refineries has only recently become a concern. Regulatory agencies have now established new and more stringent cyanide effluent limits for most wastewater discharges. One example of such a regulation is the adoption of a cyanide effluent limit of 0.025 mgL in the San Francisco Bay region in northern California.3 This cyanide limit is based on the established detection limit of total cyanide, which includes free and complexed forms of cyanide. The U.S. Environmental Protection Agency (USEPA) water quality criteria for cyanide in salt water is currently 0.001 mgL, but this limit is below the level of detection for most laboratories.3 Other states, for example, Ohio, have also established stringent cyanide limits for certain industries based on waste load allocations aimed at controlling stream toxicity. Petroleum refineries are among the industries regulated. This chapter describe cyanide occurrence in refinery waste streams and potential cyanide control methods, including end-of-pipe treatment and upstream source control. The chapter also includes a case study to evaluate cyanide control alternatives at a refinery that must meet stringent effluent limits. Preliminary capital and operation and maintenance (O&M) cost estimate are presented as well.