This document is a report on a study of errors in spelling which high school students in 48 states, the District of Columbia, and Canada have made in their writing, with special reference to the words most frequently misspelled, their relative frequency, and the kinds of spelling errors which the student made. An analysis of the different words misspelled and the number of times each word was misspelled shows that most of the words were misspelled only rarely, while a comparatively few words were misspelled much more frequently. Five major groups of errors were noted: (1) misspelling of endings of words, (2) misspelling of vowels, (3) misspelling of homonyms or near homonyms, (4) misspelling of consonants,and (5) misspelling of prefixes and combining forms. An outline of the kinds of spelling errors made in grades 9-12 is included for reference. (CK)