In this work, experiment results indicating that CR-39 can be employed as along-term alpha-scpectrometer are shown. Tracks due to alpha-particles reaching the detector at angles close to the normal of its surface and having known energies were produced by means of exposing CR-39 sheets to thin films of uranium and thorium placed at convenient distances. These tracks were analysed by using an automated system. Both the area of the tracks and thier mean optical intensity were measured. Our results indicate these two parameters can be used in order to obtain information about the alpha-particle energy (E). The reliability of the use of CR-39 as an α-spectrometer as well as its employment in radon daughters dosimetry are discussed. © 1995.