Resumo. In this article, it is studied the deforestation of ‘castanha-do-brasil’ (Bertholletia excelsa) from the Brazilian tropical rainforest with emphasis on the valuation of social costs imposed on society by the reduction and the loss of forest cover from 1998 to 2008. To measure the social costs, the concept used was of Marshall economic surplus, which measures the level of welfare consumers and producers. From 1998 to 2008, the estimated average social costs were of R$ 11.6 million per year. The social costs falling 63 % on producers and 37 % on consumers. In conclusion, both, supply and demand, lose with damages in the Brazilian tropical rainforest.