This brief article describes the strengths of local participation and the limits of local knowledge in the context of a long term research and development project in Eastern Amazonia which focuses on the subsistence and economic value of non-timber forest products for rural communities. The benefits and shortcomings of local knowledge to ecological research are outlined. Suggestions are made on how the significant gaps in local knowledge can be complemented by more conventional biophysical methods. The use of long-term ecological methods along with PRA are described while highlighting the utility of PRA when used in conjunction with other quantitative methods. The paper also points out the dilemma facing the researcher, that is whether to give priority to publishing research results for an outside audience, or making the information accessible to the local people.