Both the use of the insanity plea and subsequent acquittals appear to occur infrequently. Successful pleas appear to relate more to the psychiatrist's recommendations than to the defendant's prior criminal record, sociodemographic characteristics, history of mental hospitalization, or the nature of the current offense. Acquittees tend to be predominantly white and male, with relatively short hospitalization histories and charged with a wide range of crimes. The extent to which acquittees are hospitalized varies by jurisdiction, as does the length of hospitalization. Matched groups of felons and people acquitted through the insanity defense show similar rearrest rates. However, insanity acquittees appear to be rehospitalized more often. Further research and systematic data collection are recommended. Footnotes, 2 tables, and 17 references.