This paper describes the theoretical basis, experimental technique, and experimental evaluation of a new method of analysis called "high concentration active enzyme centrifugation". It extends by up to four orders of magnitude the upper concentration limits at which the technique of "active enzyme centrifugation" can be used for analysis of enzyme structure. This new theory is largely based on certain properties of Gaussian curves which we have described in previous publications [Wei, G.J., & Deal, W.C., Jr. (1976) Anal. Biochem. 75, 113-121; Anal. Biochem. (1978) 87, 433-446]. One of the most important aspects of this development is that it extends the concentration range upward so that experiments can be performed on enzymes in the active polymeric forms corresponding to their in vivo states. Furthermore, this expansion includes the range in which most enzymes go through all their association-dissociation transitions from one polymeric form to another. Hence, the method can be used to define the various concentration-dependent transitions and also to ascertain which of the various polymeric forms of an enzyme are active, under various conditions. This method also retains the many favorable characteristics inherent in the active enzyme centrifugation technique. In studies with lactate dehydrogenase, the results from this method of band sedimentation were identical within experimental error (about 1.5%) with results from conventional boundary sedimentation velocity studies.