Radiation effects on the mechanical behavior and the microstructure of pure her, titanium polycrystals have been investigated. Results have been analyzed in the frame of a dispersed obstacle hardening model and compared to those previously obtained for pure metals with a fcc or bee structure. such as Cu and I'd or Fe. respectively. Differences in the defect accumulation rate and the dose dependence of hardening are discussed in terms of possible irradiation hardening mechanisms for the hcp structure. (C) 2002 Elsevier Science B.V. All rights reserved.