AbstractTwo new tree variants, namely Acacia hybrid and second-generation Acacia mangium, have been introduced in plantation forests in Sarawak, Malaysia, and their wood qualities were examined. The mean basic density of Acacia hybrid was comparable with Acacia mangium. However basic density and strength properties of second-generation A. mangium were significantly lower compared to Acacia hybrid. The mean fibre length and fibre wall thickness in the hybrid were found to be greater than that of second-generation A. mangium. Fibre diameter and fibre lumen diameter of Acacia hybrid were smaller compared to second-generation A. mangium. Runkel and slenderness ratios of Acacia hybrid and second-generation A. mangium fibres showed that they were suitable for pulp and paper production. Acacia hybrid was more resistant to Coptotermes curvignathus attack than second-generation A. mangium. A laboratory soil block test showed that Acacia hybrid and second-generation A. mangium were moderately durable timbers. In summary, marked differences in wood properties and qualities were observed between Acacia hybrid and second-generation A. mangium.