We evaluated the new UniCel DxH 800 hematology analyzer (Beckman Coulter, Miami, FL) vs the Cell-Dyn Sapphire (Abbott Diagnostics, Santa Clara, CA) using 156 pediatric specimens in Microtainer tubes (Becton Dickinson, Franklin Lakes, NJ). The CBC and differential showed good interinstrument correlation, including WBCs (r = 0.995), RBCs (r = 0.992), hemoglobin (r = 0.998), mean corpuscular volume (r = 0.988), platelets (r = 0.997), neutrophils (r = 0.988), lymphocytes (r = 0.984), monocytes (r = 0.815), eosinophils (r = 0.840), basophils (r = 0.049), and nucleated RBCs (NRBCs; r = 0.906). In the instrument vs 400-cell manual differential comparison, the DxH 800 and Sapphire showed comparable performance for nearly all parameters except for NRBCs, for which the DxH 800 correlated better (r = 0.989) than the Sapphire (r = 0.906). We also compared clinical efficiency by determining whether flagged specimens showed abnormalities on a peripheral blood smear as defined by International Council for Standardization in Haematology criteria. The efficiency of the DxH 800 was 78.0% vs the Sapphire at 68.1%. Both instruments showed identical sensitivity (91.1%), but the specificity for the DxH 800 (71.9%) was higher than that of the Sapphire (57.3%).