The compound growth function of Warren (W. G. Warren, 1980. Tree-Ring Bull. 40:35-44) represented an attempt to develop a model-based approach that standardized tree ring width sequences and was more flexible than the monotonic functions that were then commonly used. While the idea was conceptually attractive, operational difficulties of fitting hindered its use as a practical tool. The paper describes the modifications, and what are believed to be improvements, that have recently been made to the method, and which have led to an interactive computer program by which the fitting of the model to any sequence of ring widths may be readily accomplished. The approach also permits the location of both positive and negative departures from a trend (releases and suppressions, respectively) and estimation of the rate of rung-width increase or decrease. For illustration it has been applied to a sample of red spruce (Picea rubens Sarg.) cores from Whiteface Mountain, New York.