The study examined the effects of item format, self-concept and anxiety on response changing behaviour. Four hundred undergraduate students who offered a counseling psychology course in a Nigerian university participated in the study. Students' answers in multiple--choice and true--false formats of an achievement test were observed for response changes. Results indicated that more changes were made in true-false than in multiple-choice test items, and students having moderate trait anxiety made significantly more changes than those having low or high trait anxiety. Academic and general self concept was not found to have significant influence on response changing behaviour. (Contains 5 tables.)