This paper analyzes a typical school spelling task in terms of an information processing model of spelling performance. Based on principles embodied in a computer simulation program previously reported (SPEL by Simon and Simon) the model proposed here has been expanded to try to account for many more kinds of student error than were possible with the original model. It explores the nature of the speller's internal representation of the word to be spelled, the information one must have in memory about the target word in order to produce a correct spelling, and the organization of the processes available to use the information to produce a spelling and to verify its accuracy. Examples of errors from children's spelling tests are used to discuss sources of errors in terms of the model. Ways in which the model may be adapted to explain performance in other kinds of spelling tasks and some implications for instruction and curriculum design are suggested. (Author/HOD)