Methods for investigating the influence of an early developmental process on a later process are discussed. Conventional growth modeling is found inadequate but a general growth mixture model is sufficiently flexible. The growth mixture model allows prediction of the later process using different trajectory classes for the early process. The growth mixture model is applied to the study of progress in reading skills among first-grade students that collected data from about 1,000 children. How the development of phonemic awareness during kindergarten influences the development of word recognition in first grade was the specific focus of the analysis. The approach is found to be a useful tool for studying the relationship between two processes. Instead of predicting growth in the later process by the growth factors of the earlier process, a latent class variable with classes corresponding to the prespecified growth shapes was used to predict growth in the later process. (Contains 2 figures, 3 tables, and 19 references.) (Author/SLD)