The Sysmex pocH-100i automated hematology analyzer was evaluated at St. John's Regional Health Center, Springfield, Missouri, USA, and compared with the Sysmex KX-21N. The pocH-100i is a compact, fully automated hematology analyzer with the capability for simultaneous analysis of 17 parameters in the whole-blood mode. The touch screen liquid crystal display presents results, and the 3 histograms for white blood cell (WBC), red blood cell (RBC), and platelet (PLT) counts can be printed along with numerical results. This study was performed to provide necessary information for the US Food and Drug Administration study of allowing the product's use in the North American marketplace. The pocH-100i processes approximately 25 samples/hour, uses 2 reagents, and provides for testing in a closed-tube environment, while using only 15 microL in the whole-blood mode and 20 microL in the predilute mode. Using hydrodynamic focusing on the pocH-100i improves the accuracy for RBC and PLT measurements. Our evaluation included studies of correlation, carryover, reproducibility, linearity, and stability. Results with the pocH-100i showed good correlation with those from the KX-21N for the following parameters: WBC; numbers and percentages of lymphocytes, mixed cells (monocytes, eosinophils, and basophils), and neutrophils; RBC; hemoglobin; hematocrit; mean corpuscular volume; mean corpuscular hemoglobin; mean corpuscular hemoglobin concentration; PLT; red cell distribution width SD (RDW-SD); RDW coefficient of variation; and mean platelet volume. Carryover and reproducibility were well within the manufacturer's specifications. The pocH-100i showed linearity over the entire range for all parameters studied. A reference range for a healthy population was also established. We conclude that the overall performance of the pocH-100i is excellent and compares favorably with that of the KX-21N.