From 57th annual meeting of the Federation of American Societies for Experimental Biology; Atlantic City, New Jersey, USA (15 Apr 1973). An analysis is presented of the one-compartment calculator previously used, and examples are given of its performance in situations where inflow and outflow rates are known. A two-compartment calculator is described, and examples are given of the much improved estimates of inflow and outflow that result from its use. In the two- compartment procedure, preliminary observations are made of plasma glucose specific activity in the steady state, and these are subjected to compartmental analysis. Elements of this two-compartment system are utilized to create the calculator for use in the nonsteady state. The whole procedure can be carried out by hand, using a desk-top machine. (LMT)