BACKGROUND: We evaluated the performance of the GEM Premier 4000 (Instrumentation Laboratory, USA), a new blood gas/electrolytes/co-oximetry analyzer, according to the Clinical and Laboratory Standard Institute (CLSI) guidelines. METHODS: Within-run precision, total-run precision, linearity and sample-related carryover were analyzed using quality control materials at three different concentration levels for each analytes. Correlation was compared with the routinely used NOVA CCX2 (Nova Biomedical, USA) with patients' whole blood samples. RESULTS: The within-run and the total-run precisions of the GEM Premier 4000 showed very low CV of 0.04~4.40% and 0.06~4.11%, respectively, in all parameters except the lactate, which had CV of 5.58% in Level 1 QC material. The system showed a good linearity (r2=0.997~1.000, systemic error=0.00~0.20%) for all items. Sample-related carryover was -4.35%~0.15%. In comparison with the NOVA CCX2 instrument, correlation was high in all parameters with the r value ranging from 0.983-0.999 except for carboxyhemoglobin (r=0.804) and methemoglobin (r=0.010) whose concentrations were in the lower level. CONCLUSIONS: GEM Premier 4000 showed good analytical performance required for blood gas analyzer in its precision, linearity, sample-related carryover, and close correlation with NOVA CCX2. It fulfills most of the requirements for both point-of-care and laboratory use.