The development of phonological and orthographic processing was studied from the middle of Grade 1 to the end of Grade 4 (age 6; 6-10 years) using the effects of regularity and of lexicality in reading aloud and in spelling tasks, and using the effect of pseudohomophony in a silent reading task. In all the tasks, signs of reliance on phonological processing were found even when indicators of reliance on orthographic processing appeared. Multiple regression analyses were conducted to determine which early skills predict later reading achievement. Pseudoword and irregular word scores were used as measures for phonological and orthographic skills, respectively. Only middle of Grade 1 phonological reading skills accounted for independent variance in end of Grade 4 orthographic skills. Conversely, from the middle to the end of Grade 1, and from the end of Grade 1 to the end of Grade 4, both orthographic and phonological skills accounted for independent variance in later orthographic skills. In the prediction of phonological skills, only the unique contribution of earlier phonological skills was significant. Thus, phonological and orthographic processing appear to be reciprocally related, rather than independent components of written word recognition. However, very early reliance on the phonological procedure seems to be the bootstrapping mechanism for reading acquisition.