Fundamental to this monograph is an attempt to understand the nature of individual difference in word and nonword reading by connecting three literatures that have developed largely in isolation from one another - the literature on acquired sdyslexia, difficulties in learning to read, and precocious reading. These literatures and studies of both developmental dyslexia and garden variety poor reading in children are examined to show how careful attention to methodological and conceptual issues can highlights similarities and differences across this diverse group of readers.