A detailed physiological analysis was made of an oil palm density x fertilizer experiment established on a deep peat soil near Teluk Intan, Perak. Data on above-ground vegetative dry matter production, leaf area and leaf area development, flowering, bunch dry matter production and bunch composition were collected from the time of first flowering up to the 17^th year after planting. Three planting densities (120, 160 and 200 palms ha^-1) were combined with 18 factorial fertilizer treatments. From data on leaf area, vegetative, bunch and total dry matter production, it was possible to derive the efficiency of radiant energy conversion to dry matter and the partitioning of dry matter between vegetative and reproductive biomass as well as between oil and non-oil components of dry matter. The influence of planting density on the extent of biomass turnover was assessed. Optimum densities for bunch yield were calculated as a function of age from single palm yield response to density. The proportions of assimilated carbon used for dry matter production, growth respiration and maintenance respiration were also calculated. Maintenance respiration per unit biomass was seen to decrease as a function of increasing palm age and density. The evaluated dry matter production and gross assimilation were compared with outputs from a simulation model. The results are discussed and compared with those of other studies in the literature.