The erythrocyte sedimentation rate (ESR) is a nonspecific screening test to assess elevations of acute phase proteins that occur in various acute and chronic diseases. The recommended method is based on the Westergren method. Other technologies to measure ESR have been developed, including centrifugation-based methods. We compared a centrifugation method (ESR STAT PLUS, Hema Technologies, Lebanon, NJ) with the current Westergren method (Sediplast ESR system, Polymedco, Cortlandt Manor, NY) at 3 ESR levels (0-20, 21-60, and >60 mm/h) in a pediatric population and found correlation coefficients of r=0.63, r=0.83, and r=0.43 respectively. The centrifugation ESR exceeded the Westergren ESR by a small but significant amount in the 0-20 mm/h range, where most normal ranges fall. The 2 methods were also compared in blood samples from patients with sickle cell disease, who tend to have lower ESRs owing to impaired rouleau formation. In the sickle cell group (n=39; r=0.87), the centrifugation ESR consistently exceeded (97% of time) the Westergren ESR. This study identifies the differences in ESR results using 2 methods in general and specific pediatric populations.