OUTLINE: This is a dose escalation study. Each treatment course is 28 days in length. On days 1-3 pentostatin is administered over 5 minutes by IV bolus and followed 1 hour later by a 1 hour infusion of cordycepin IV. An escalating dose of pentostatin is given with a fixed dose of cordycepin until the desired level of adenosine deaminase inhibition is observed. After this is determined, a dose escalation schedule for cordycepin is initiated to determine the maximum tolerated dose (MTD) when given in combination with pentostatin. The MTD is determined by the number of patients who exhibit dose limiting toxicity and the severity of the toxicity.