Abstract: The growth and development analyses and also the tests made to determine the physico- mechanical properties of fast-grown korean pine (Pinus koraiensis S.et Z.) taken from a planta- tion established 30 years ago at Tsao-ho-kou Experimental Forest in Liaoning province,North- east China have been carried out.The data presented indicate that the fast-growing trees have pass the juvenile stage earlier,and there are no significant differences of strength properties be- tween the wood of fast-grown planted stands and the adult wood of slow-grown natural stands. From the viewpoint of modern materialistic biological science,i.e.the teaching on unity and interdependence between vegetation and all the conditions of its existance,the authors discuss the results with particular reference to the relationship between growth and development of the stand and the variations of timber quality. It is concluded that under the control of the forester,when a tree is growing rapidly,it could be expected to produce wood of reasonably high strength,due to the fact that it has reached the adult stage earlier.This means that a fast rate of growth does not have a deleterious effect on quality of the wood.The quality depends not on the rate of growth but on the stage of development.