It has been pomted out that tree processors are required for realizing high levels of productivity in delimbing and bucking. We theoretically analyzed the conditions necessary for the introduction of processors by comparing full-tree logging with tree-length logging. We assumed that tree-length logging consisted of felling and delimbing by chain saw, tractor skidding, and bucking by chain saw, and that full-tree logging consisted of felling by chain saw, tractor skidding, and delimbing and bucking by processor. The results were as follows: 1) The productivity of chain-saw delimbing varies over a wide range according to tree species, chain-saw horsepower, and the quantity of branches. 2) The break-even point is determined by the size of trees and skidding distance. 3) When the D.B.H. of trees is 15〜20cm, tree-length logging is more useful with increasing skidding distances. Thus it is necessary for a dense road-network with short skidding distances for the introduction of full-tree logging with processors, especially when the trees are not over 20cm in D.B.H. 4) When the D.B.H. is more than 20〜25cm, full-tree logging is always more suitable. 5) If the payload of full-tree skidding increases, or if the moving time of the chain-saw operator increases on steep slopes, the efficiency range of full-logging will widen.