From 1978 to 2002, 30 patients presenting hairy-cell leukemia were seen in two different hospitals. We reviewed clinical, biological and therapeutic data. At diagnosis, the median age was 67.8 years; 47% were clinically asymptomatic, 12 patients had anaemia, 15 thrombocytopenia (platelets<100,000/mm3). A treatment was required for 29 patients. At the end of the study, 27 patients are alive and none died because of the disease. This study confirms the good prognosis of hairy-cell leukemia, especially since the advent of new therapeutics such as purine analogs. Based on the results in this series, we examined the different aspects of the disease referring to diagnosis, treatment and prognosis.