A corollary of the principle that reading comprehension depends on language comprehension is that word skill plus language comprehension skill produces reading comprehension skill. This corollary points to word decoding as being the major source of differences in skilled reading. Various data supporting this claim have been collected from measuring vocalization latency, latency of same-different judgments to letter strings, decision times to judge whether printed words name orally presented targets, time to decide whether a word target is present in a word string, time to decide whether a semantic target is present in a word versus a picture, and time to decide whether a string of words contains a semantic target. In addition, it has been found that differences between reader groups have been largest when production was required and when a semantic decision was required. These facts all suggest the conclusion that speed of accessing the phonological representation of a word is a major skill component differentiating readers. (JM)