BACKGROUND: Synchron LX20(Beckman Coulter, Fullerton, USA) is an automated chemical analyzer introduced in 1998. It is still not completely evaluated on clinical fields, is set in the Asan Medical Center for the first time in Korea. We evaluated the performance of the analyzer before routine use to prevent critical errors, to confirm the manufacturer's instructions, and to establish a specific data system for our institute. METHODS: For glucose, BUN, creatinine, total protein, albumin, uric acid, cholesterol, total bilirubin, direct bilirubin, ALT, AST, LD, gamma-glutamyltransferase(gamma-GT), CK, amylase, lipase, Na, K, Cl, CO2, Ca, phosphorus and Mg, within-day precision, between-day precision, degree of correlation, linearity, recovery rates and reportable ranges were completely or partly analyzed. Specimen selection, specimen preparation and the statistical methods followed the guidelines of National Committee for Clinical Laboratory Standards as much as possible. The calculations were performed with computer software, EP_Suite(MarChem Associates, Concord, USA). RESULTS: The within-day coefficients of variations(CVs) of most items were less than 5.0%. Ninety six percent of items showed between-day CVs less than 10.0%. All items had %relative nonlinearities less than 2.5%. The correlation coefficients of BUN, creatinine, AST, ALT, total bilirubin, direct bilirubin, gamma-GT, glucose and UA exceeded 0.975. The recovery rates were analyzed for BUN, creatinine, glucose and UA, and all were in the range of 98.2% to 102.3%. Reportable ranges were wide enough for all items. CONCLUSIONS: Linearity, precision, recovery rates and reportable ranges were satisfactory. A few CVs were relatively large due to the significant effects caused by the small differences among the measured values of low concentration specimens. Some items showed low correlation coefficients probably due to insufficient device familiarization period.