23 newly diagnosed patients affected by cutaneous T-cell lymphoma were treated with sub-cutaneous interferon alpha-2a to evaluate the therapeutic efficacy and the toxicity of this agent. IFN was administered daily with dose escalation from 3 to 18 million units for 12 weeks; thereafter, patients induced into complete (CR) or partial (PR) remission were given IFN at maximal tolerated dose 3 times weekly for 6 or 9 months. The objective tumor response was observed in 17 patients (74%): 8 (35%) were CR and 9 (39%) were PR. A 74-yr-old patient died because of neutropenia and sepsis at the end of induction phase, while receiving IFN at dose of 18 million units. Disease stage is the initial feature predictive of response to IFN therapy. The dose schedule of this study was well tolerated: only 3 patients developed liver toxicity, while leukopenia was evident in 6 patients. Only 2 CR patients have relapsed, 18 and 24 months from response; the remaining 6 CR patients are in continuous complete remission with a median follow-up of 41.8 months. 6 PR patients have progressed from 8 to 17 months after response, and in the 3 PR patients not yet progressed the response duration ranges from 20 to 24 months. In conclusion, interferon alpha-2a is a very effective agent in therapy of untreated cutaneous T-cell lymphoma with an overall response rate of 74%.