In 1991, there are numerous proven therapies for the treatment of hairy-cell leukemia. Since none have been proven to be curative, it is important that all be considered, as individual patients might need to undergo a series of sequential treatments with each. In fact, some elderly patients with minimal splenomegaly and relatively normal blood counts might require no therapy. Splenectomy has a role in rapid reversal of severely depressed blood counts in association with a systemic infection; however, growth factors might soon replace this role of emergency splenectomy. Treatment with recombinant interferon results in few complete remissions, but with normalization of peripheral blood counts in over 80% of patients. In the original interferon alfa-2b study of 195 patients, only three of the 159 patients achieving a normalization of their blood counts have subsequently died. Treatment with deoxycoformycin either after interferon or initially has resulted in an apparent complete remission rate of approximately 60%, but recent follow-up analyses suggest that hairy cells persist within the bone marrow; however, patients seem to remain in a clinical remission. Treatment with 2-chlorodeoxyadenosine shows little toxicity and a high apparent complete remission rate. However, review of the posttreatment bone marrow specimens remains to be done, and longer follow-up is necessary to assess true differences in the degree of response from interferon or deoxycoformycin treatment. Advances in therapy over the past decade have led to significant benefits for patients with hairy-cell leukemia.