Reading is acutely sensitive to the amount of space between letters within a string. In the present investigation, we explore the impairment caused by increasing interletter spacing when reading single words and nonwords aloud. Specifically, 2 hypotheses are tested: (a) whether increasing interletter spacing induces serial processing while reading aloud and (b) whether this serial processing results from an increased reliance on a serial sublexical mechanism similar to that implemented in dual route models of reading. Implications of the present results for understanding basic processes in reading are discussed with particular reference to different types of serial processing in reading aloud and the role of attention in reading. (Contains 3 footnotes, 2 tables, and 1 figure.)