The research program was designed to provide a more basic understanding of the mechanism and rates of removal of organic materials from waste waters by biological processes. Pure compound feed materials were used with the exception of a series of tests on sewage solids obtained from the Minneapolis-St. Paul Sewage Treatment Plant by centrifugation of primary effluent. Two model reactor systems were used to measure rates of substrate removal. The film flow reactor, characterized by a stationary biological slime layer, was used to study removal kinetics under conditions where mass transfer may be a limiting factor. A well mixed batch reactor was used to study rates of removal under conditions where biological processes are rate controlling. Rates of substrate degradation and carbon removal are reported for each of the pure compounds using acclimated innoculum. Rate data from batch reactors are expressed in terms of microbial growth rate coefficients. Rate data from the film flow reactor is reported as the quantity of substrate removed per unit of slime surface per unit of time.