Interaction of nine provenances of Acacia mangium Willd. were studied at three sites of the Philippines such as Lubuagan, Vintar in Ilocos Norte (Region – 1), Mapuyo, Mobo in Masbate (Region-5) and Lantapan Malaybalay in Bukidnon (Region-10). The sites were climatically, edaphically and topographically different from each other. The provenances studied were 13233 (Walsh’s Pyramid, Qld.), 13235 (Mourilyn Bay, Qld.), 13236 (Kurrimine, Qld.), 13238 (Tully Mission Beach, Qld.), 13240 (Ellerbeck Rd. Cardwell, Qld.), 13241 (Broken Pole Creek, Qld.), 13242 (Abergowrie SF, Qld.), 13460 (Oriomo River, Qld.), 13621 (Piru Ceram, Indonesia).

Analysis of variance for diameter and height showed significant variations due to provenance, site, and provenance-site interactions. All the provenances except one (13621) showed the best growth at Bukidnon site due to main effect. The significant provenance-site interaction was found at Masbate site which was mostly due to the remarkably different growth behaviour of the provenance 13621.