We have studied retrospectively patients with chronic lymphocytic leukaemia (CLL), at Ryhov, Jönköping, Sweden during a 10-year-period. This unselected cohort (n = 59) from a well-defined geographical area is suitable for describing the natural course of the disease. The CLL was diagnosed incidentally in the majority of cases. Median-age at diagnosis was 71 years and the male:female ratio was 1.3:1. The diagnosis was based on morphology in 66% and in 33% immunophenotyping specified the diagnosis of B- or T-CLL. At diagnosis 66% were in Rai-stage O/I or Binet-stage A. There were 36% untreated patients and their median-survival was 108 months compared with 84 months for the whole cohort and 72 months for the treated patients. Malignancies were seen in 31% and infections in 83%. Intercurrent diseases played an important role in the survival. During the observation time, only 54% of the deceased patients had died due to the CLL.