This study was condcted to evaluate the yield and the log breaks down methods of 20 tropical hardwood species from the construction area of the Balbina Hidroeletric and forest reserve ZF-2. A minimum of 5 logs per species were analysed to obtain th date abot the subject of this study. The average yield of the species varied between 41, 9% and 61,6%. Six of these species showed average yield higher than usually estimated range of 45% to 55% considerate for tropical hardwoods. Among the analysed species, logs of Brasimum rubescens (Pau rainha) and Manilkara huberi(Maçaranduba), showed the highest degree of difficult to saw. The medium diameter , the conicity degree of the logs and the basic density when individually analyzed had great influence on the degree of difficult to saw logs of different species. The mathamatical equations presented in this study allow the volume estimation of sawn wood produced from logs of any of the species studied.