The edge effect on DBH (diameter at breast height) in two adjacent Pinus radiata D. Don stands was modeled as a function of both the distance from the stand edge and Hegyi's competition index. The modeling was applied to edges with external-competition pressure and on free edges. In both edge types, the incorporation of the Hegyi's competition index in the modeling significantly reduced the residual variation. This modeling showed that the intensity of the intraspecific competition varies between stands. Particularly, the trees in younger stands are more sensitive to the effects of competition than in older stands. However, the intensity of the competition does not vary between edge aspects of stands. The results of the study related to the depth of edge effect can be useful for stratifying stands when getting more precise estimates of trees and stand parameters from sampling are required, and for defining the width of the buffer strip in experimental units used for long-term field assays. (C) 2008 Elsevier B.V. All rights reserved.