OUTLINE: Patients receive cladribine (2-chlorodeoxyadenosine; 2-CdA) daily for 5 days every 4 weeks for a maximum of 6 courses; response is assessed after every 2 courses. Patients in complete remission or with stable disease discontinue treatment and are followed; those with disease progression at any time are removed from study. Patients are followed every 2 months for 1 year, every 4 months for 1 year, every 6 months for 1 year, and annually for 2 years.