The erythrocyte sedimentation rate (ESR) is a nonspecific indicator of disease activity and is often used by clinicians in assisting diagnosis and follow-up of many inflammatory disorders. The Westergren method is considered the standard method for measuring ESR. Recently, many automated instruments have become available to address laboratory safety and time efficiency. We validated the Streck ESR-Auto Plus instrument (Streck, Omaha, NE) using the Sediplast (Polymedco, Cortlandt Manor, NY) Westergren method as the reference method. Blood samples collected in 113 EDTA tubes were transferred into Sediplast vials and Streck high-altitude vacuum tubes for measuring the ESR. There was good correlation between the Sediplast and Streck methods (0.95) using Pearson correlation. The y-intercept was at 6.5 using linear regression, indicating systematic bias with a mean difference of 7.13 using the t test (P < .0001). We modified our reference ranges to rectify the systematic bias found during validation.