The biomass of Rhizophora apiculata Bl. was measured within a 25 m 2 sample plot in a mangrove at Phuket Island on the west coast of Thailand. The total biomass above the ground of this 15 years-old stand was estimated to be 159 t dry matter ha −1. The annual increment in the form of trunks, branches and prop roots was estimated to be 20 t ha −1yr −1 during the last year of growth. By means of a simple marking technique, leaf turn-over rate was found to be 0.7 yr −1 and leaf production was 6.7 t ha −1yr −1. Buds, flowers and propagules contributed very little to annual production. Total net production was estimated to be 27 t dry matter ha −1yr −1 or 6.9 g ash free dry matter m −2day −1. The biomass of prop roots, trunks, branches and leaves as well as leaf areas were determined for 1 m horizontal levels. Prop roots formed 39% of total biomass above the ground.