Previous studies of myeloma immunoglobulin synthesis and tumor cell number, using a marker kinetic approach, have increased knowledge about body burden of tumor cells, kinetics of myeloma cell growth, and response to chemotherapy. On the basis of these observations, we have developed a clinical staging system that permits accurate estimation of total myeloma cell number in patients who have not had specialized immunosynthetic measurements. We have incorporated this clinical staging into a nationwide time-sharing computer network called the Myeloma Study System (MSS). With the MSS we are able to establish a file for each patient, keep track of changes in tumor cell number with treatment, and evaluate toxicity. This resource should afford an excellent test of the value of cellular kinetics for the planning and uniform evaluation of cancer chemotherapy.