Purpose: Although α-fetoprotein is one of the most commonly used tumor markers in Korea, most of the radioimmunoassay kits for α-fetoprotein have been imported from foreign countries. The purpose of this study was to evaluate the performance of a recently developed domestic immunoradiometric kit for α- fetoprotein (Riakey AFP IRMA CTR, Sin-Jin Medics, Seoul, Korea). Materials and Methods: We evaluated intra- and inter-assay precision, recovery rate, parallelism, and sensitivity of serum α-fetoprotein measurement using Riakey AFP IRMA CTR kit. The values of α-fetoprotein measured by Riakey AFP IRMA CTR kit were compared with those measured by two foreign commercial kits (α-fetoproteina of Radim and α-feto.riabead of Abbott). Results: Intra-assay coefficients of variation on three different levels were 5.3% for 18.9 ng/ml, 3.4% for 133 ng/ml and 1.6% for 330 ng/ml. Inter-assay coefficients of variation were 9.7% for 20.9 ng/ml, 3.2% for 137 ng/ml and 4.1% for 330 ng/ml respectively. Recovery rate tests on all three different levels showed within 100±10%. Parallelism was also good and the sensitivity was 0.63 ng/ml. There was strong correlation between the measurement of α-fetoprotein by Riakey AFP IRMA CTR and that by two foreign commercial kits(r=0.98). Conclusion: The first Korean domestic immunoradiometric kit for α-fetoprotein, Riakey AFP IRMA CTR, performed well for clinical use. (Korean J Nucl Med 2000;34:353-9)