This current work had as objectives to study the relation between the basic density and resistance of the tropical wood submitted to the test of Janka hardness of the extremes and faces on the conditions green and dry at 12% of the moisture content. Eight forest species collected from Distrito Agropecuário da SUFRAMA located at the municipality of Manaus, AM, were used. The experiment was realized in the Wood Engineering Laboratory of the Forest Products Department of the Instituto Nacional de Pesquisas da Amazônia, attending the following steps: a) realization of the essays of basic density and Janka hardness used by COPAN norm; b) statistic treatment of linear regression in order to appraise the influence level of density on wood hardness. The results obtained show that the hardness of the wood represented by its capacity in offering smaller or brigger resistance to the penetration of a semi-sphere, is strictly related to the density.