Carbon dioxide reactivities of powdered samples of Acacia and Eucalyptus wood chars were measured thermogravimetrically at 900-degrees-C and the effects of carbonization conditions (temperature, heating rate and soaking time) and wood species were determined. The results showed that the reactivity decreased with increasing carbonization temperature and soaking time. Chars prepared under rapid carbonization (heating rate: 30-degrees-C min-1) were found to be more reactive than the chars produced by slow carbonization (heating rate: 4-degrees-C min-1). In comparison to Eucalyptus wood chars, the Acacia wood chars exhibited higher reactivity.