THE PSYCHIATRIC STATUS SCHEDULE (PSS), USED IN ALL THE INTERVIEWS, FOCUSED ON SYMPTOMS PRESENT AT THE TIME OF THE INTERVIEW OR IN THE RECENT PAST. FOR THOSE PRISONERS THE PSYCHIATRIST JUDGED TO BE IMPAIRED, A DIAGNOSIS WAS MADE WITH THE SAME CRITERIA USED IN THE PSYCHIATRIST'S OFFICE. OF THE 33 MEN, 12 (36.4 PERCENT) HAD NO MENTAL DISORDER; NINE (27.3 PERCENT) HAD ONLY DRUG OR ALCOHOL PROBLEMS; AND THREE (9.0 PERCENT) HAD EVIDENCE OF PSYCHOSIS OR NEUROSIS. DISORDER PREVALENCE RATES FOR INMATES WERE SIGNIFICANTLY GREATER THAN THOSE RATES ESTIMATED FOR THE SAME COUNTY'S GENERAL POPULATION AS INDICATED BY THE COUNTY'S PSYCHIATRIC REGISTER. THEFT WAS THE MOST FREQUENT CRIME, BUT WAS EVENLY DISTRIBUTED AMONG THE DIAGNOSTIC GROUPS. THOSE INMATES WITH DRUG OR ALCOHOL PROBLEMS WERE SERVING LONGER SENTENCES THAN THOSE WITH NO MENTAL DISORDER, WHO IN TURN WERE SERVING LONGER SENTENCES THAN THOSE WITH SOME PSYCHIATRIC DIAGNOSIS. RESULTS INDICATED BOTH THAT A SUBSTANTIAL PERCENTAGE OF SENTENCED PRISONERS HAVE SOME DISTINGUISHABLE PSYCHIATRIC DISORDER AND THAT DISORDERS ARE MORE PREVALENT THAN IN A NONPRISON POPULATION. FOUR POTENTIAL CAUSAL MODELS WERE DISCUSSED. FIRST, PSYCHOLOGICAL DISORDERS' PRESENCE MAY PRECIPITATE CRIME COMMISSION. SECOND, CRIME COMMISSION MAY PRECIPITATE A MENTAL DISORDER. THIRD, AN UNKNOWN FACTOR SUCH AS EARLIER EXPERIENCES OR CHILDHOOD MAY PRECIPITATE BOTH MENTAL DISORDER AND CRIMES. FOURTH, THERE MAY BE NO RELATIONSHIP BETWEEN CRIME AND MENTAL DISORDER. THE THIRD MODEL IS ARGUED TO BE MOST FREQUENTLY APPROPRIATE. USUAL PSYCHIATRIC TREATMENT METHODS MAY NOT WORK FOR THESE INDIVIDUALS, YET THEIR PROBLEMS MAY BE MORE SEVERE THAN IN A NONCRIMINAL POPULATION AND THEREFORE MAY REQUIRE SPECIAL REHABILITATION PROGRAMS. THE SIZABLE MINORITY WITH NO EVIDENT DISORDER INDICATES THAT PSYCHOPATHOLOGY DOES NOT EXPLAIN ALL CRIMINAL BEHAVIOR. FURTHER RESEARCH INTO THIS GROUP'S CHARACTERISTICS IS RECOMMENDED. TABLES, NOTES, AND REFERENCES ARE INCLUDED. (CFW)