Colorectal cancer remains the second leading cause of cancer death in the western hemisphere. During the past several decades information regarding epidemiology, etiology and associated factors regarding colo-rectal cancer in humans has been collected through study of experimental colonic tumors in animal models. Much of this work has been influenced by the use of 1,2-dimethylhydrazine as the inducing carcinogen in susceptible populations of animals, although other specific carcinogens have been used. Through application of this experimental model, knowledge of dietary, immunologic, and bacterial factors has been realized in the etiology of colo-rectal cancer. This review details methodology and results of developing experimental models as they pertain to human colo-rectal cancer. © 1987.