The theory is discussed of individual tree compatible taper equations which predict the diameter along the stem as a function of tree height, diameter at breast height, and length, and which can be integrated to give a total volume equation equal to an existing volume equation. Existing non-linear form of compatible taper equations were estimated for Pinus radiata D. Don but were unable to illustrate the neiloid shape of butt, common in old crop P. radiata. Polynomial compatible taper equations were developed to provide greater flexibility in defining tree shape. These had standard errors of estimate of diameter of 1.4 cm for young crop and 2.4 cm for old crop radiata pine, and they had all the destrable characteristics of compatible taper equations.
