A new simple immunoassay method for carcinoembryonic antigen (CEA) detection using a disposable immunosensor coupled with a flow injection system was developed. The immunosensor was prepared by coating CEA/colloid Au/chitosan membrane at a screen-printed carbon electrode (SPCE). Using a competitive immunoassay format, the immunosensor inserted in the flow system with an injection of sample and horseradish peroxidase (HRP)-labeled CEA antibody was used to trap the labeled antibody at room temperature for 35 min. The current response obtained from the labeled HRP to thionine-H(2)O(2) system decreased proportionally to the CEA concentration in the range of 0.50-25 ng/ml with a correlation coefficient of 0.9981 and a detection limit of 0.22 ng/ml (S/N=3). The immunoassay system could automatically control the incubation, washing and current measurement steps with good stability and acceptable accuracy. Thus, the proposed method proved its potential use in clinical immunoassay of CEA.