Mature T-cell lymphoproliferative disorders comprise a heterogenous group of diseases for which there is no standard therapy. These disorders are uncommon, and are usually treated similarly to their B- cell counterparts, but with less success. Nucleoside analogues have proven effective in indolent B-cell disorders but have been less well explored in T-cell malignancies. We treated 22 patients with mature T- cell lymphoproliferative diseases with 2-chlorodeoxyadenosine (2-CDA) administered as a continuous infusion at a daily dose of 4 mg/m2 over 7 days. Nineteen of the patients had received prior therapy with a median number of prior regimens of three. Eleven patients had leukemia or large granular lymphocytosis, eight patients had mycosis fungoides, and three had T-cell lymphoma. Nine patients (41%) responded to 2-CDA. Four of the patients had responses that were complete remissions, and three of these four patients remain in remission at 23, 24, and 23 months. The only important toxic effects were fever or infection, seen during 38% of courses. In conclusion, 2-CDA appears to be an effective therapy in T-cell lymphoproliferative disorders and deserves wider evaluation in this subset of patients.