Survival of 839 chronic lymphocytic leukemia patients has been reviewed in relation to a number of patient and disease characteristics. Over-all, the relative 5-yr survival rate was 44%. Studying survival by age and sex led to the following observations: Dividing age into intervals < 50, 50-59, 60-69, 70-79, and 80 yr and over, relative survival declined with increasing age; relative 5-yr survival for females was higher than that for males-50% versus 41%. This pattern of superior survival of females over males was noted in all but one of the age intervals. Survival was negatively associated with the presence of recorded clinical signs and symptoms, hematological abnormalities, and pathological bone marrow findings. Differences in survival were also found by treatment category and interval from diagnosis to initiation of treatment. Adjustment for differences in distribution of each of these variables did not materially diminish the survival differences noted by age and sex. An unexpected pattern of survival in relation to white blood count level was noted. Survival increased with increasing white blood count at diagnosis, peaking in the interval at 25,000-49,000, and decreasing after that. When survival by white blood count was adjusted for some variables which were found to be associated with survival, the gradient was still noted, though somewhat reduced.