The determination of the serum proteins of patients with colorectal carcinoma has revealed qualitative and quantitative changes in immunoglobulin levels. New information was obtained by the demonstration with our electrophoretic fractionation technique of a weak but discrete homogeneous band in the gamma-globulin zone in several cases studied. This band has been named minimonoclonal. Our studies of the determination of lactate dehydrogenase-isoenzymes (LD) in normal tissues and serum from abnormal conditions both in humans and in animal models were extended to the determination of LD isoenzyme patterns of the various types of peripheral blood cells. These studies demonstrate that the characteristic pattern of LD-isoenzymes can serve as an indication of the target cell involved in malignancy thus aiding in the diagnosis of the various types of leukemia. The determination of serum lipoprotein patterns was performed in a rare category of type 3 hyperlipoproteinemia (HLP) patients by our unique electrophoretic technique. A finding of major importance was the demonstration for the first time of an extra B-lipoprotein band in the serum of these patients which can be used as a marker to distinguish them from other HLP types by a single electrophoretic test.