Fundamental characteristics of a new plastic scintillation fiber (PSF) has been studied for four kinds of radiations, and the possibility of using the PSF as a radiation detector has been discussed. Irradiation experiments of scintillation output characteristics have been made for γ rays, x rays, fast neutrons, and α particles. Various scintillation pulse height spectra have been obtained, depending on the variations of radiation types, energies, intensities, and scintillating positions on the PSF. Position detection experiments have been also made for γ rays and fast neutrons, and a new position sensitive detector of the PSF has been proposed.