The electronic modal lymphocyte volumes of 151 patients with chronic lymphocytic leukemia (CLL) and 305 normal controls were determined by the hydrodynamically focused multi-channel Coulter TF analyser. The mean volumes of the normally distributed groups were 166 +/- 19.3 (range 126-216) fl in patients with CLL and 206 +/- 14.4 (range 126 +/- 246) fl in normal controls. The calculated cell diameters were 6.8 (6.2-7.4) micron and 7.3 (6.8-7.8) micron respectively. Our data do not support previous reports about relations between cell size and clinical stages of the Rai and Binet classifications.