In this study, the effect of heat treatment on air- dry density (D(m)), oven-dry density (D(0)), shrinkage (beta) swelling (alpha), compression strength parallel to grain bending strength (sigma(b)), modulus of elasticity (MOE) in bending, brinell-hardness (H(B)), equilibrium moisture content (EMC), chemical content and cellulose crystallinity of oak (Quercus petraea Lieb.) wood were examined. Wood specimens were subjected to heat treatment under atmospheric pressure at three different air temperature (130, 180 and 230 degrees C) and two different time levels (2 h and 8 h). The results showed that value of D(m), D(0) maximum moisture content (MMC), beta, alpha, sigma(b), MOE, sigma(cll), EMC and holocellulose ratio were decreased whereas the values of density in volume (D(b)), H(B), lignin content, 1% NaOH and alcohol solubility values increased depending on the heating temperature and the time. The changes in cellulose crystallinity of the specimens were not significant. At heat treatment process, 130 degrees C has minimum effect; on the other hand, 230 degrees C has maximum effect on all properties of treated wood. Accordingly, for heat treatment process, 130 degrees C for 2 h should be applied in place where mechanical properties are important. However, 230 degrees C for 2 h should be used in place where physical properties are preferred. Treated oak could be utilized in applications for several purposes such as musical instruments, kitchen furniture, outdoor furniture and windows frames.