Public opinion data show that the most prevalent concern expressed regarding the insanity defense is that it is a loophole through which would-be criminals escape punishment for illegal acts. This article examines the extent to which the public's perceptions of the insanity defense are consistent with newly collected empirical data. Specifically, it compares perceptions of the use, success, and outcomes associated with the insanity defense to data derived from a large-scale study of insanity pleas in eight states. The analysis reveals that the public overestimates the use and success of an insanity defense and underestimates the extent to which insanity acquittees are confined upon acquittal. The role of selective media reporting in the formation of public perceptions is discussed.