The authors present data on all insanity pleas (N = 202) in Erie County, New York, between 1970 and 1980. No demographic, criminal history, current offense, or history of mental hospitalization factor was associated with acquittal. Of the variables studied, only the recommendation of the forensic examiner was associated with the court's decision to acquit by reason of insanity. When an insanity acquittal was recommended in the examination report, conviction ensued in only 17% of the cases. The proportion of pleas that were successful varied considerably over the 10 years studied. The authors discuss the critical need for more research on the plea stage of insanity defense proceedings.