BACKGROUND: The measurement of serum erythropoietin (EPO) is useful for the differential diagnosis of polycythemia and anemia and for treatment monitoring of recombinant human EPO. Radioimmunoassay (RIA) has been used in several clinical laboratories of Korea, and recently a few manufacturers developed fully automated chemiluminescence immunoassay (CLIA). We evaluated performance of Access EPO assay (Beckman Coulter, USA) using CLIA and established reference interval for Korean adults with this assay. METHODS: The precision, linearity, limit of detection, percent carryover, comparison of Access EPO CLIA and EPO-Trac RIA (DiaSorin Ltd, UK), and establishment of reference interval were determined according to the Clinical and Laboratory Standards Institute guidelines. The quality control materials were used in the determination of precision, limit of detection, and carryover. For the reference interval, serum specimens obtained from a total of 120 healthy adults were used. RESULTS: The linearity was good (R2=0.998) from 0.5 IU/L to 732.3 IU/L and within-run and total imprecision were 2.1-4.1% and 2.6-4.1%, respectively. The lower limit of detection was 0.259 IU/L and percent carryover was 0.18%. A comparison analysis with RIA assay showed good correlation, with a correlation coefficient (R) of 0.88. The reference interval was from 2.5 IU/L to 30.8 IU/L with nonparametric method. CONCLUSIONS: The Access EPO assay provided suitable performance for linearity, precision, and detection limits for clinical laboratory. As this assay does not need radioactive isotopes and afforded a short turnaround time (<1 hr), it is expected to be clinically useful especially for the outpatients.