Further comparisons are made with felony defendants who never entered a plea of not guilty by reason of insanity (NGRI). From existing data it is unclear to what extent detention may vary if the plea is successful as compared to if it is not successful. Of all defendants who entered a plea of NGRI in Erie County, New York (Buffalo) between 1970 and 1980, 128 were institutionalized as a result of their disposition. Sociodemographic, institutionalization histories, arrest, and disposition information were collected and analyzed for all 128 individuals. The research evaluates differences in the likelihood and length of either institutionalization or incarceration and in the rates of release between successful NGRI defendants, those who entered the plea unsuccessfully, and those who did not plead NGRI. From the findings reported here the authors conclude that pleading NGRI in Erie County may not be quite as advantageous for a defendant as commonly is believed. (Publisher abstract)