CELL-DYN Ruby is a new automated hematology analyzer suitable for routine use in small laboratories and as a back-up or emergency analyzer in medium- to high-volume laboratories. The analyzer was evaluated by comparing the results from the CELL-DYN((R)) Ruby with the results obtained from CELL-DYN Sapphire . Precision, linearity, and carryover between patient samples were also assessed. Precision was good at all levels for the routine cell blood count (CBC) parameters, CV% being <or=2.6, except for platelet count (PLT) at the low level with CV% of <or=6.9%. The CV% for reticulocyte percentage was highest at the low level (10.4). In a comparative study, the CELL-DYN Ruby results showed a good correlation (R(2) >or= 0.98) with CELL-DYN Sapphire for the CBC parameters. For the absolute reticulocyte count, R(2) was 0.82. In the white blood cell (WBC) differentials, the between-days precision was good for all parameters (CV%: <or=8.0), except basophil percentage and absolute basophil count (CV%: <=or 31.8 and 31.3, respectively). Additionally, in the commercial control sample with the low WBC count (2.5 x 10(9)/l), the precisions in the WBC differentials were <or=16.9%. The cell types that occur in low numbers showed higher CVs, as expected. The methodological comparison of the WBC differential parameters of neutrophils, lymphocytes, and eosinophils showed excellent correlations (R(2) >or= 0.97), and the correlation coefficient for absolute monocyte count and monocyte percentage were 0.91 and 0.87, respectively. For absolute basophil count and basophil percentage the correlations were weaker (R(2) = 0.46 and 0.34, respectively). Carryover was minimal for all the parameters studied. The linearities of WBC, red blood cell, PLTs, and hemoglobin were acceptable within the tested ranges. In conclusion, the results of the evaluation showed the performance of CELL-DYN Ruby to be good.