Advances in the understanding of biochemical and molecular processes associated with cellular growth and differentiation, as well as colonic carcinogenesis hold promise for the development of new diagnostic and therapeutic modalities for this disease. Altered glycosylation of cell surface and secreted glycoconjugates appear to be useful markers in differentiating normal from malignant colonic tissue. New information regarding deletion and inappropriate expression of several blood group-related carbohydrate antigens as well as the synthesis of unique cancer-related carbohydrate structures has been derived from the use of monoclonal antibody technology, and may lead to more sensitive and specific screening tests and targeted therapies. Several glycoprotein markers for colon cancer have been studied whose diagnostic accuracy may surpass the limited sensitivity and specificity of traditional markers such as CEA. Colorectal cancers contain numerous quantitative and qualitative differences in metabolic and synthetic enzyme activities compared with normal colonic mucosa, which may be of potential importance in designing chemotherapeutic regimens or for following disease activity. Other cancer-associated markers, such as increases in orthinine decarboxylase activity and crypt cell labeling reflect abnormal proliferative activity and may be correlated with premalignant states. Studies of protooncogene expression and certain chromosomal deletions will provide insight into mechanisms of carcinogenesis and may also serve to define high-risk individuals. It is likely that as the biochemical and molecular mechanisms underlying malignancy are further delineated, cancer-associated markers will be defined that will improve diagnostic and more importantly, therapeutic efficacy.