To develop a coherent description of the knowledge and processes involved in skillful word recognition, a study was devised in which 16 adults participated in four related experiments. The purpose of the first experiment was to examine some basic aspects of the processing of words, pseudowords, and nonwords and to discover basic differences in processing that might underlie the word advantage (the relative perceptibility of words, compared to that of nonwords). The second experiment assessed the contribution of whole-word and letter cluster cues to the word advantage. The other two experiments focused on whether the word advantage can be wholly explained in terms of response bias or sophisticated guessing. The study yielded these results: the word advantage is mediated by perceptual processes; in terms of basic information processing, the processing of words and nonwords appears to be quite similar; and although identity and positional information are extracted by separate mechanisms, they exhibit a mutual dependence. The results are compatible with a criterion-bias model that attributes the word advantage to the relationship among single letters and lexical units in memory. (A bibliography and appropriate tables are appended.) (MAI)