The automated Sysmex M-2000 was evaluated according to the ICSH (International Committee for Standardization in Haematology) protocol. After dilution of packed cells with cell-free plasma, blood cell counts were linear. The overall precision of the measured parameters was good; the CV's ranged between 0.64% and 2.06%. The carry-over was negligible; platelets showed the biggest carry-over with 0.25% in the Whole Blood Mode, while red blood cells (RBC) showed a carry-over of 0.55% in the Prediluted Mode. 300 clinical samples were measured on the Sysmex M-2000 and the Sysmex CC-700 with PL-100, and the results were compared. The coefficients of correlation for white blood cells (WBC), red blood cells (RBC), haemoglobin and haematocrit were greater than 0.99; platelets showed an r of 0.982. Comparison of the results from the Sysmex M-2000 trimodal leukocyte distribution with a manual 100 cell differentiation showed a close correlation for lymphocytes (r = 0.948), and neutrophils (r = 0.931). The middle cell fraction corresponding to monocytes, eosinophils and basophils showed a correlation with r = 0.703. Pathological samples showed no interference with the blood count. Leukocyte counts less than 1000 x 10(9)/l did not effect the measurement of haemoglobin. During the period of evaluation, no instrument malfunctions occurred. Because of its precision and reliability, the Sysmex M-2000 is well suited for routine work and stat analysis in medium-sized laboratories.