The influence of the temperature on tropical wood (meranti) samples was studied in the diploma thesis. Changes to selected chemical, physical and optical properties of wood were monitored. The wood was thermally loaded at temperatures of 20, 160, 180, 200 and 220°C. The percentage of extractives, lignin, holocellulose, cellulose, hemicelluloses and density was defined in thermally modified samples. In the original (untreated) wood sample (20 °C), was the biggest amount of hollocelullose (77,5 %). The results were evaluated using statistical methods, analysis of variance and Duncan´s test. The obtained results show that the increasing temperatures causes changes in the chemical, physical and optical properties of tropical wood. With increasing temperature, an increase in the content of extractives, lignin and cellulose was recorded. In holocellulose and hemicelluloses, a decrease in their content was found with increasing temperature.