Abstract: It is well known that most of the wood based panel properties are mainly related to the specific gravity of the panel.For a long time,the oriented strand board(OSB) industry has been searching for ways to reduce board density while the board properties still can fulfill the standard requirements.Lower board density means less raw material needed and lower pressure during hot pressing.In this paper,with and without horizontal density distribution panels were made.The implications of the density variations on bonding will be analyzed.Experimental results concerning the density and property relationships of structurallydefined strand assemblies will be presented.The influences of density variations on board properties including internal bond strength,bending strength and thickness swell will be discussed.