Trace element analyses by energy dispersive X-ray fluorescence measurements were made using synchrotron radiation from a dedicated electron storage ring at the Photon Factory in Japan. The continuum or the monochromatic beam was used for excitation. A crystal monochromator or two types of mirror systems were used for monochromatic excitation. A high signal to background ratio was attained with the crystal monochromator, while the highest absolute detectability was achieved with the mirror system. The minimum detection limita obtained from thin samples are of the order of 0.1 ppm or less than 0.1 pg. Furthermore the signal to background ratio was significantly improved by using an X-ray mirror as a sample support in which, external total reflection of exciting X-rays occured.