Distribution and Potency of Keruing (Dipterocarpus spp.) on the Island of Siberut, West Sumatra. Nur. M. Heriyanto and M. Bismark. Distribution and potency of Dipterocarpus spp. (keruing) were studied in Siberut Biosphere Reserve area, covering Sot Boyak and Bekemen forest village, Siberut National Park, West Sumatra. Six research plots of 50 m x 50 m (0.25 ha) were laid down. The results showed that Dipterocarpus spp. density at the tree level were 31 trees/ha at Sot Boyak and 38 trees/ha at Bekemen forest village with important value index of 63.83% and 77.54% respectively. The strongest association of other trees to Dipterocarpus spp. were Hopea dryobalanoides Miq., Baccaurea bracteata Muell. Arg. and Endospermum diadenum Miq. as reflected respectively by 0.69, 0.67 and 0.56 of Ochiai index. Dipterocarpus spp. were commonly located on the slopes and ridges. The best grouping was on 50-59% Slopes. Slope relationship with the population distribution of Dipterocarpus spp. showed by the equation of Y = 5.83 ln (x) + 3.44 with R2 = 0.90. Regeneration of Dipterocarpus spp. in natural forest is highly dependent on the recruitment population. Saplings recruitment population was 556 individuals/ha, and seedling was 3,434 individual/ha.