An algorithm is described for balancing the steady-state operation of a separative cascade of the up/down type wherein each head stream is fed upward one or more stages, and each tail stream is fed downward one or more stages. The cascade incorporates refluxing and multiple feed points. Of primary importance is the treatment of multiple isotopes, which requires an iterative solution procedure. Only half of the separation factors can be arbitrarily specified, the other half are found as part of the solution process.