This paper presents results of investigations into possibility of using polymethyl methacrylate to reinforce wood degraded by Phellinus pini (Thore) Fr. fungus. It was found that impregnation of wood with the resin causes an increase in mechanical properties. Nevertheless this increase is relatively greater for wood degraded by biological agents than for undamaged wood. The behaviour of wood-resin system after artificial ageing in laboratory conditions was observed. The strength of wood treated with the resin was lower after artificial ageing than the strength of wood without ageing. Similar tendencies of changes were observed both in the case of wood degraded by biological agents and in the case of undamaged wood.