Wood of broadleaved species, modified with polymethylmethacrylate (85-95% content) were tested in air at 20° and 90°C; at a temperature range from -50 to +80°C; at a moisture range from 45 to 95%; specimens were also exposed on the south side of a roof for a year. The results showed that laboratory aging treatments did not significantly affect the physical and mechanical characteristics of the wood-plastic composites, but that exposure on the roof for a year resulted in checking of the composites along the grain, with corresponding impairment of the strength properties. -- AATA