Chronic lymphocytic leukaemia (CLL) is generally considered to be a disease of the older population. The aim of this retrospective study was to determine whether younger subjects with CLL (< or = 55 years of age) were different from older patients in their clinical features and prognoses. A total of 198 CLL patients registered to the centre were analyzed: 47 (24%) were 55 years of age or younger and 37 who were followed up regularly were included in the study. The male/female ratio was significantly higher in young patients (3.7 vs. 1.51; p = 0.02). More young patients were asymptomatic than old patients at initial presentation (38.3% vs. 28.5%; p > 0.05). The clinical features, laboratory findings, the distribution of both age groups into clinical stages, and the overall response rate to treatment were similar. The median time to follow-up was 62 months. During this period, 14 of the young patients died (48.3%); all were males. The median survival was longer in the young (64.5 vs. 47 months, p > 0.05). The 5-year survival rate of young patients was more than the old (57% vs. 31%), but the 10-year survival rates did not differ between the two groups (7% vs. 8%). The rate of CLL-related death was higher in young patients (71% vs. 59%; p > 0.05). Univariate analysis revealed no prognostic factor which could influence the survival probability of young patients. In this study, the prognostic values of some variables could not be assessed accurately as the number of regularly followed young patients was low and some data were missing. However, it is expected that survival will be longer in young CLL patients, so the search for different curative treatment strategies will continue.