This paper presents equations developed to predict the height to live crown base of six species in the central western Willamette Valley of Oregon. Weighted nonlinear regression was used to fit a separate logistic equation for each species. The predictor variables are total tree height, crown competition factor in trees with larger diameter at breast height than the subject tree, stand basal area, and diameter-height ratio. The equations will be used in two ways: 1) to estimate crown ratio on trees for which that measurement is missing, and 2) to simulate crown change in a single-tree/distance-independent growth and yield model. Application of these equations will be most reliable in stands that are free from thinning effect.