This study seeks to investigate whether the biodiversity conservation of the Sinharaja rainforest in Sri Lanka can be economically justified solely in terms of its non-timber forest products (NTFPs) extraction potential as claimed by some recent research. A variety of methods and techniques were deployed including a botanical inventory survey, a crosssectional ethnobotanical survey, an ethnobotanical log-book survey and an ethnozoological survey. Several aspects relating to the NTFPs use: a) valuing the total inventory stock, the total extractable stock limit, the potential flow and actual flow; b) estimating the wild meat flow; c) seasonality of harvesting; d) sustainability issues; e) influence of phytosociological characteristics; f) influence of socio-economic characteristics; and g) forest accessibility; and h) market accessibility were investigated. Biophysical and socio-economic factors influencing the NTFPs value were investigated using a regression analysis. The impact of the NTFPs extraction on the regeneration of the natural population was investigated using three forest sites, a proximal site, a distant site, and a logged forest. The local peoples' perception about the sustainability of NTFPs harvesting was analysed using logit regression analysis. A geographic information system was used to investigatet he influenceo f accessibilityt o the forest and to the marketplace from the villages on the forest products flow. Finally, the NTFPs value was compared with alternative land-clearance use and timber use values. The results indicate that the NTFPs extraction value is insufficient on its own to economically justify the rainforest biodiversity conservation in Sri Lanka, and perhaps elsewhere. There is also some doubt about the long term sustainability of forest products extraction. The study concludes that the rainforest conservation will have to be justified by a full total economic value (use and non-use values) appraisal, together with other scientific and ethical reasoning and cannot be promoted solely on the basis of non-timber extraction value.