There was studied the effect of millimetre radiation (MMR) on the germination processes of seeds of medicinal plants: safflower (Carthamus tinctorius L.) and Echinacea purpurea (L.) Moench) during ex situ conservation. Separate effects of MMR (wavelength 5.6 mm; power density 6.6 mW/cm2; exposures 8 and 30 min) and combined with reduced temperature (RT) (2-4oC) on seeds after their long-term storage in a plant genetic bank were examined. The factors were applied in direct (MMR+RT) and reverse (RT+MMR) combinations to reveal the protective and reparative effect of MMR on old seeds. The effect of MMR and RT on morphophysiological and biochemical parameters of seeds and seedlings (seed germination energy and germination capacity, seedling root length, seedling dry biomass, peroxidase enzyme activity in seedling roots) after storage was determined. According to these parameters after treatment of seeds with MMR, stimulation of growth processes was found. Protective and reparative effect of MMR on seeds was revealed. Protective effect of MMR is better expressed, both effects indicate the increase of seed viability with MMR under abiotic stress. The method is recommended to increase the viability of seeds of some medicinal plants during ex situ conservation.