The anerobic degradation of organic matter to methane is a complex interaction of basically three groups of bacteria (fermentative, acetogenic, methano-genic). This report provides a description of the different types of anerobic treatment that have been developed. The processes described in this report are the (1) Conventional, (2) Contact, (3) Upflow filter, (4) Expanded Bed, (5) Sludge Blanket and (6) the Anaerobic Rotating Biological Contactor. A summary of the application of anerobic processes on a variety of wastewaters is also covered, along with the process parameters used to control the operation. Operational parameters covered, along with the process parameters used to control the operation. Operational parameters covered are (1) pH and alkalinity, (2) nutrient requirements, and (3) temperature effects on biological processes. Biodegradation of Organic Compounds by the Anerobic Processes are covered along with the common tests used to predict biodegration. Toxicity effects, Inhibition, Antagonism and Synergism and their methods of measurement are fully evaluated.