This paper evaluated immobilization of anti-C-reactive protein (CRP) monoclonal antibody on a quartz crystal microbalance (QCM) when 2-aminoethanethiol (AET), 4,4'-dithiodibutyric acid (DDA), and 11-mercaptoundecanoic acid (MUA) were deposited on the gold surface of QCM. In all monolayers, anti-CRP antibodies were immobilized such as Langmuir types because it had been introduced with a corresponding active group. According to the Langmuir isotherm equation a(max), the maximum immobilized amounts of anti-CRP antibody were 4.27, 2.72, and 3.74 pmol/cm(2), respectively. Although the immobilized amount of anti-CRP antibody was highest on the AET monolayer, the amount of antigen-antibody binding between the anti-CRP antibody and the CRP was highest on the MUA monolayer. CRP was detected from negative to positive levels when the calibration curve was achieved using MUA monolayer.