Two trials of external quality assessment were performed in 2001. Thirteen test items of immunoassay with six control materials were surveyed. The response rate of external quality assessment for Immunoassay Subcommitee were 94.3% and 94.5% of selected institutions. Six control materials were consisted of 5 home-made pooled sera and 1 commercial control sera.The results are summarized as follows. 1. Laboratories participating in external quality control program of immunoassay were 233 to 241 laboratories and the response rate were 94.3% and 94.5% in 2001. 2. Chemiluminiscence immunoassay autoanalyzer was widely introduced comparing to previous years and now it is the most popular analyzer in the field of immunoassay testing. 3. Still some test items show big variations of the test results of the same control material. But, generally the quality of the participating laboratories seems to be thought being improved.