DEFENDANTS WHO ARE FOUND TO BE, AS A RESULT OF MENTAL ILLNESS, INCOMPETENT TO STAND TRIAL ARE OFTEN TREATED WITH PSYCHOACTIVE OR PSYCHOTROPIC DRUGS. THESE ARE DEFINED AS COMPOUNDS AFFECTING THE MIND, BEHAVIOR, INTELLECTUAL FUNCTIONS, PERCEPTION, MOODS, AND EMOTIONS; INDIVIDUAL CATEGORIES OF THE DRUGS INCLUDE: ANTIPSYCHOTIC DRUGS FOR THE TREATMENT OF SCHIZOPHRENIA; ANTIDEPRESSANT DRUGS; LITHIUM FOR THE TREATMENT OF MANIA; AND ANTIANXIETY DRUGS. SUCH DRUGS HAVE ALLOWED INCREASING NUMBERS OF PATIENTS ON MAINTENANCE DOSAGES OF MEDICATION THAT INHIBIT THE MORE SEVERE MANIFESTATIONS OF THEIR ILLNESS TO FUNCTION IN THE COMMUNITY RELATIVELY FREE OF PSYCHOTIC SYMPTOMS. SOME COURTS, MISTAKENLY ASSUMING THAT PSYCHOTROPIC DRUGS PRODUCE A 'CHEMICAL SANITY' THAT IS UNACCEPTABLE FOR PARTICIPATION IN A TRIAL, HAVE ADOPTED THE 'AUTOMATIC BAR RULE' FOR DEFENDANTS UNDER TREATMENT INVOLVING PSYCHOACTIVE MEDICATION. SURVEYS SHOWED THAT THE AUTOMATIC BAR RULE IS IN OPERATION IN AT LEAST 13 STATES. DATA FROM A STUDY OF 143 NEW YORK CITY DEFENDANTS RETURNED TO COURT BETWEEN JANUARY-JUNE 1974 AS COMPETENT TO STAND TRIAL BUT REQUIRING CONTINUING PSYCHOTROPIC MEDICATION FORM THE BASIS OF A DISCUSSION OF THE USE AND EFFECTS OF EACH OF THE MAJOR CLASSES OF PSYCHOTROPIC DRUGS. EXAMINATION OF THE AUTOMATIC BAR RULE COVERS CONSTITUTIONAL CHALLENGES IN RELATION TO EQUAL PROTECTION OF THE LAW, CONCLUSIVE PRESUMPTION, PROCEDURAL AND SUBSTANTIVE DUE PROCESS, SPEEDY TRIAL, AND CRUEL AND UNUSUAL PUNISHMENT. IT IS RECOMMENDED THAT THE AUTOMATIC BAR RULE BE ABANDONED, THAT EACH DEFENDANT'S COMPETENCE ON DRUGS BE INDIVIDUALLY DETERMINED, THAT SPECIAL PROCEDURES AND JURY INSTRUCTIONS BE APPLIED IN APPROPRIATE CASES, THAT HOSPITAL AND DETENTION FACILITY PRACTICES WITH RESPECT TO PSYCHOTROPIC DRUG ADMINISTRATION BE REVIEWED AND REVISED, AND THAT PSYCHIATRISTS BE MADE AVAILABLE FOR EVALUATION OF DEFENDANTS AND CONSULTATION WITH JUDGES. NOTES AND REFERENCES ARE INCLUDED. (AUTHOR ABSTRACT MODIFIED).