Certain categories of grammatical errors made by 42 teacher trainees at Lund University in Sweden are described and explained. Each student was asked to write two summaries in English, one an account of a book that appeared on a list of books for extensive reading and the other an account of a 40-minute tape recording in the language laboratory, "A Bear Called Paddington." The two exercises tested reading comprehension and listening comprehension, respectively. The errors were corrected, and a typology of the grammatical errors was established. Native speakers of English were then asked to evaluate the errors according to a four-point scale: (1) "uncertain," (2) "acceptable in colloquial and careless language," (3) "wrong but comprehensible," and (4) "wrong and incomprehensible." The categories of errors were as follows: (1) verb phrase, (2) noun phrase, (3) prepositions, (4) concord, (5) pronouns, (6) word order, (7) clause connection, (8) adjectives and adverbs, (9) complementation, and (10) numerals. The majority of errors were committed in the areas of verb phrase, noun phrase, prepositions, and concord. (CFM)