To analyze the sustainability and carrying capacity of a mangrove forest, we studied the profiles of species composition and biomass from the riverside to inland. A belt transect (25× 180 m) divided into 9 plots was established in compartment 46, in the Matang Mangrove Forest Reserve, Perak, Peninsular Malaysia. Five tree species were distributed in the transect. Rhizophora apiculata showed the highest density, followed by Bruguiera parviflora, B. sexangula, R. mucronata and Avicenia alba. From the riverside to inland, the structure changed from pure R. apiculata stands to mixed Rhizophora-Bruguiera stands. The mean aboveground biomass of all the plots was 316 Mg ha-1. The largest and smallest volumes for biomass were 558 Mg ha-1 on the riverside and 144 Mg ha^-1 inland, respectively. The values tended to be higher in R. apiculata-dominant stands. If a larger productive area could be set up where R. apiculata would predominate, i. e. an area at a lower ground level, a larger sustainable amount of biomass for firewood and charcoal use could be produced. The annual dead biomass, which is supplied to the forest floor as nutrients for aquatic life, was 5.1 Mg ha-1. While stocked biomass is more valuable to a local economy than the dead biomass, the contribution of the fallen trees (dead biomass) to habitats and nutrients for aquatic life must be evaluated exactly in the future.