ALTHOUGH SEX CHROMOSOME ABNORMALITIES ARE FOUND IN GREATER PROPORTIONS AMONG PERSONS WITH MENTAL ILLNESS THAN AMONG THE GENERAL POPULATION, IT IS UNCLEAR WHETHER A CAUSAL CONNECTION CAN BE MADE BETWEEN GENOTYPIC DISORDER AND BEHAVIORAL DISORDER. CERTAIN PATTERNS, HOWEVER, DO EMERGE FROM AN ANALYSIS OF DATA OBTAINED IN EPIDEMIOLOGICAL AND CLINICOPATHOLOGICAL STUDIES. IN ABNORMAL CHROMOSOME SYNDROMES, PATHOLOGICAL PROGRESS IS DEPENDENT UPON THE DISTRIBUTION, PROLIFERATION, AND GENETIC CAPACITY OF ABERRANT CELLS. MANY CASES OF CHROMOSOME ABNORMALITY ARE MOSAICS, HAVING LESS THAN ALL BODY CELLS AFFECTED, AND HAVING A CONSIDERABLE AMOUNT OF VARIATION IN DEVELOPMENT. SERIOUS EFFECTS MAY BE LIMITED TO THE REPRODUCTIVE ORGANS, AS IN ANEUPLOIDY, OR MAY BE WIDESPREAD, AFFECTING THE LIMBIC SYSTEM AND THE PANCREAS. WHEN BRAIN AND GLAND CELLS ARE AFFECTED, BIOLOGICALLY INFLUENCED SOCIAL FAILURE MAY RESULT. CLEARLY, SUCH SYNDROMES ARE NOT THE ONLY CAUSE OF VIOLENT BEHAVIOR, AND THE CONNECTION IS NOT INEVITABLE. VIOLENT BEHAVIOR IS DEPENDENT UPON A COMBINATION OF FACTORS WHICH VARY WITH TIME. ANY SPECIFIC CAUSATION CAN ONLY BE DETERMINED AFTER INTENSIVE EXAMINATION OF INDIVIDUAL GENOTYPES AND SURVEILLANCE OF HIGH RISK GROUPS. A COMBINED PURSUIT OF DEVELOPMENT STUDIES ON THE NEUROBIOLOGY OF BEHAVIOR IS PREFERRED TO ANY CONTINUED RESEARCH ON AN ASSOCIATION BETWEEN CHROMOSOME ABNORMALITY AND VIOLENCE. APPENDED MATERIAL DISCUSSES THE SOCIOLEGAL CONSIDERATIONS OF RESEARCH IN BEHAVIORAL ILLNESS AND THE SAFEGUARDING OF SUBJECTS' RIGHTS. TABULAR DATA AND REFERENCES ARE PROVIDED. (TWK)