The present study investigated the dynamic developmental relations between phonological awareness and decoding ability in two groups of 3- and 4-year-old children (N = 2,513) from the Head Start Impact Study (U.S. Department of Health and Human Services, 2002-2006) who were followed through the end of kindergarten. Children were randomly assigned to either receive Head Start or not. Using latent change score modeling methods, I tested several hypotheses regarding developmental influences among these literacy skills: (1) phonological awareness and decoding skills are developmentally correlated but do not influence one another; (2) phonological awareness influences decoding ability; (3) decoding ability influences phonological awareness; or (4) phonological awareness and decoding ability simultaneously influence one another. Results indicated that decoding ability predicted change in phonological awareness for 3- and 4-year-old children. The same trend emerged when the 3- and 4-year-olds were examined separately. Mixture modeling suggested no evidence for more than one latent class for both Head Start participants and controls, indicating an absence of differing developmental trajectories. The implications of these findings are discussed. (author abstract)