The efficacy and toxicity of 2-chlorodeoxyadenosine (2-CdA) in cutaneous T-cell lymphoproliferative disorders was examined. Between February 1991 and April 1996, 25 patients with relapsed or refractory cutaneous T-cell lymphoproliferative disorders (24 mycosis fungoides or Sezary syndrome, one Ki-1+ anaplastic large cell lymphoma) were treated with 2-CdA initially administered by continuous intravenous infusion at a dose of 0.1 mg/kg/d for 7 days (13 patients). The infusion duration was subsequently reduced to 5 days (9 patients) because of prohibitive hematologic toxicity. Three patients were treated at the same daily dose by bolus injection over two hours for 5 days. Cycles were administered at 28 day intervals. Seventeen patients received more than one cycle. An overall response rate of 24% was achieved. Three patients (12%) had a complete response with a median duration of 4.5 months (range, 2.5 to 16). Three (12%) had a partial response with a median duration of 2 months (range, 2 to 4). Nineteen patients (76%) had no response. The most significant toxicities encountered were myelosuppression (64%) and infectious complications (64%). 2-CdA has activity as a single agent in patients with previously treated relapsed T-cell lymphoproliferative disorders.