Comparison of volume production, basic density and stem quality between Acacia mangium and Acacia auriculiformis grown in Zanzibar. Volume production, basic density and stem quality of 6-y-old Acacia mangium and A. auriculiformis grown in Zanzibar were compared. Twenty-one plots (11 plots for Acacia mangium and 10 for A. auriculiformis ) were established and used for data collection. From each plot one to two trees free from obvious defects were selected for basic density determination. Cores were then extracted from the selected trees using an increment borer. Basic density of the cores was determined by the water displacement method. Height and diameter data were used for volume estimation. Stem quality was assessed using the scoring method, 4 being the best and 1 the worst. At age 6 y, diameter and height growth did not vary significantly (p = 0.05) between the two species. More than 50 m3 ha"1 volume production was achieved in both species. The average volume weighted basic density values for A. mangium and A. auriculiformis were 570 kgm"3 and 617 kgm"3 respectively. The basic density values for the two species differed significantly (p = 0.05). Stem quality was better in A. mangium than in A. auriculiformis. Based on density, A. auriculiformis can be recommended for fuelwood production whereas A. mangium should be recommended for transmission and building poles due to its good stem form.