An overview is given of the absolute flux calibration of the ISOCAM detectors. The flux calibration is based on observations of standard stars selected from the Ground Based Preparatory Programme, for which Kurucz stellar models are available. No dependencies of the responsivity on different configurations of the camera were found. No trend of changing responsivity is found throughout the mission for the SW and LW detectors. There exists a decreasing responsivity of about 5% for LW during the orbit.