The followings are the results for external quality assessment (EQA) in immunoserology for 2001: 1. Evaluation of EQA was done in 2 trials in June and December, about 94% of laboratories participating average 8.4 items. 2. In C-reactive protein (CRP), rheumatoid factor (RF) and anti-streptolysin O (ASO) tests, 40.4%, 55.1% and 51.4% of the participating laboratories respectively have used qualitative assays, mainly latex agglutination. And 55.5%, 42.3% and 40.3% of the participating laboratories have used quantitative assays, turbidimetric immunoassay or nephelometry in CRP, RF and ASO tests respectively. The quantitative results were quite variable according to the methods or reagents. 3. Over 85% of participating laboratoreis have used imunoassay including enzyme immunoassay (EIA), microparticle EIA (MEIA), chemiluminescence immunoassay (CIA), immunochromatography (ICG) or radioimmunoassay (RIA). False negative results were more frequently found in the laboratories using reverse passive hemagglutination (RPHA) for HBsAg and found in the laboratories using ICG for anti-HCV. Many laboratories reported falsely negative for the specimen with positive anti-HIV. 4. The sensitivity of the reagents and criteria of interpretation were considered to be evaluated in Widal test and serological tests for syphilis.