The prevalence of writing errors made by third-year medical students from the class of 1981 at a large midwestern medical school was studied. The papers of 253 students taking family medicine were evaluated for spelling, grammar, and punctuation errors. Four types of grammar errors and seven punctuation errors were analyzed, and each word misspelled was counted only once, even if it appeared several times. Spelling errors were found in 184 papers (73 percent), averaging 3.68 misspellings per paper, while grammar errors occurred in 75 papers (30 percent), averaging 2.16 per paper. Punctuation errors were discovered in 153 papers (60 percent), with 3.5 errors on average. Only 14 percent of the papers had no errors. Fifty-five percent had errors in more than one category, and 23 percent had errors in all three categories. It is concluded that more than half of the medical students had problems with written English, and nearly one quarter committed simple errors in spelling, grammar, and punctuation. Of the nine words most commonly misspelled, only one was a technical medical word. It is recommended that serious consideration be given by medical faculties to reintroducing formal written papers in the medical school curriculum. (SW)