Electron paramagnetic resonance (EPR) spectra of Pinus sylvestris and Larix decidua seeds show that priming with PEG+200 mg kg(-1) gibberelic acid (GA(3)) results in appreciably higher free radical contents than in unprimed control samples. Only relatively minor changes in the free radical levels were observed in seeds primed with K(+) salts. However, both priming treatments have been reported previously to result in faster germination rates compared to controls without changing the germination percentage. In measurements on individual seeds of L. decidua, there were no significant differences between the mean free radical levels in viable and non-viable seeds within each treatment group. Thus, the elevation in free radical levels in the PEG+GA(3) treatments appear to be a direct consequence of the priming treatment and do not correspond to the initiation of germination.