The dosimetry is described for an investigation of the induction of somatic aberrations in Tradescantia occidentalis by substantially mono-energetic neutrons in the energy range 100 keV to 15 MeV, by 200 keV X-rays and cobalt-60 gamma-radiation. Spectrometry was carried out for both neutrons and X-rays. Neutron fluence was measured by uranium fission chambers. Two types of ionization chamber were employed for dose measurement. One chamber was manufactured of CH-plastic and filled with acetylene and the other of graphite and filled with carbon dioxide. Dosimetry for X- and gamma-radiation was by means of lithium fluoride thermoluminescent dosemeters calibrated against a Victoreen ionization chamber.