Depletion lymphocytapheresis therapy using the continuous-flow separator was used in twenty-two cases of chronic lymphocytic leukemia. Applying the Montserrat scoring system, a prediction can be made, to a good approximation, whether the patient will be a "responder" or a "non-responder" to leukapheresis. Criteria have been formulated for decisions on when depletion lymphocytapheresis is absolutely or only relatively indicated, on the basis of total scores from 2 through 6 using the Montserrat criterion.