Although elevation of the white blood cell (WBC) count at diagnosis of chronic lymphocytic leukemia (CLL) appears to predict shortened survival, its significance later in the course of the disease remains unclear. We reviewed all cases of CLL seen in our center between 1980 and 1999 to evaluate the frequency and clinical significance of WBC elevation > 100 x 10(9)/L. CLL was confirmed according to standard diagnostic criteria and data was collected from diagnosis, occurrence of WBC > 100 x 10(9)/L, and last follow-up. 235 consecutive patients with CLL were identified; 94 were excluded. 141 included patients had a median age of 61 years and median WBC 19.7 x 10(9)/L at diagnosis. Median follow-up for all patients was 56 months, and median survival was 104 months. 41 patients (29%) had > or = 1 episode of WBC > 100 x 10(9)1/L, occurring at a median of 38 months from diagnosis. Compared to controls matched for modified Rai stage, development of a WBC > 100 x 10(9)/L did not predict inferior survival (median 107 vs. 101 months, p = 0.72). We conclude that the occurrence of a WBC count > 100 x 10(9)/L in patients with CLL does not shorten the survival, and patients require therapy only if other indications for treatment are present.