THE TAPPING TEST UTILIZES A TELEGRAPH KEY AND AN AUTOMATIC COUNTING DEVICE, AND IS GENERALLY CONSIDERED SENSITIVE TO MINIMAL BRAIN DAMAGE. IN STUDY 1, THE TAPPING TEST WAS ADMINISTERED TO A SAMPLE OF ANGLO-AMERICAN PROBATIONERS, 35 MINORS AND 19 ADULTS AND SCORES WERE COMPARED WITH AGE-MATCHED NORMALS. A SIGNIFICANT CORRELATION WAS FOUND BETWEEN TAPPING AND AGE, WITH ADULTS EVIDENCING FASTER RATES THAN JUVENILES. INTELLIGENCE QUOTIENT (IQ) SCORES WERE NOT RELATED TO TAPPING FOR JUVENILES BUT WERE FOR ADULTS. APPLICATION OF NORMS FROM PREVIOUS STUDIES YIELDED INCIDENCE-OF-ORGANICITY ESTIMATES THAT RANGED BETWEEN 21 AND 48 PERCENT; A RANGE TOO WIDE TO BE USEFUL IN SCREENING FOR ORGANICITY. THE AGE AND IQ RELATIONSHIPS FOUND FOR DELINQUENTS AND ADULTS SUGGEST THAT DELINQUENTS MAY ENGAGE IN A RELATIVELY LENGTHY DEVELOPMENTAL SEQUENCE. IN STUDY 2, THE TAPPING TEST WAS ADMINISTERED TO 127 MALE AND FEMALE DELINQUENTS, 13 TO 20 YEARS OLD, OF ANGLO-AMERICAN AND NON-ANGLO-AMERICAN ETHNICITY. ANALYSIS OF DATA INDICATES THAT MALES TAPPED FASTER THAN FEMALES, AND OLDER OFFENDERS TAPPED FASTER THAN YOUNGER OFFENDERS. AN UNEXPECTED SEX/ETHNICITY INTERACTION WAS FOUND: ANGLO-AMERICAN FEMALES SCORED SIGNIFICANTLY LOWER THAN ANGLO-AMERICAN MALES, WHILE NON-ANGLO-AMERICAN FEMALES SCORED AS WELL AS NON-ANGLO-AMERICAN MALES. THE RESULTS WERE ONLY PARTIALLY CONSISTENT WITH THOSE OF OTHER STUDIES, CONSEQUENTLY FURTHER RESEARCH WILL BE NECESSARY TO ESTABLISH THE DIAGNOSTIC UTILITY OF THE TAPPING TEST. THE ESTABLISHMENT OF NONDELINQUENT ADOLESCENT NORMS FOR SEX, AGE, AND ETHNIC SUBGROUPS AND THE IDENTIFICATION OF ADDITIONAL FACTORS SUCH AS DEPRESSION WHICH MAY INFLUENCE TEST SCORES ARE RECOMMENDED. REFERENCES ARE INCLUDED. (JAP)