THE STUDY IS BASED ON 394 YOUNG MALES (TARGET BOYS) FROM A WORKING CLASS AREA OF LONDON, ENGLAND. THE BOYS WERE RECRUITED AT AGE 8-9 FOR A 12-YEAR STUDY OF DELINQUENCY DEVELOPMENT. POLICE FILES ON ALL PERSONS CONVICTED OF CRIMINAL OFFENSES IN ENGLAND AND WALES WERE SEARCHED FOR THE NAMES OF THE TARGET BOYS, THEIR PARENTS, AND THEIR SIBLINGS. A SIGNIFICANT ASSOCIATION WAS FOUND BETWEEN CRIMINALITY AMONG THE TARGET BOYS AND CRIMINALITY AMONG THEIR PARENTS AND SIBLINGS. CRIMINALITY WAS CONCENTRATED IN A MINORITY OF FAMILIES. OUT OF 394 FAMILIES, 44 ACCOUNTED FOR NEARLY HALF OF ALL CONVICTED INDIVIDUALS (184 OUT OF 392). SEVENTEEN FAMILIES ACCOUNTED FOR NEARLY ONE-HALF OF ALL RECORDED CONVICTIONS (561 OUT OF 1,197). EXPLANATIONS FOR THE FINDING THAT CRIME APPARENTLY RUNS IN THE FAMILY ARE SOUGHT IN DATA FROM THE OFFICIAL RECORDS AND FROM OTHER ASPECTS OF THE 12-YEAR STUDY, BUT THE DATA DO NOT SUPPORT ANY SINGLE EXPLANATION OF HOW VULNERABILITY TO CRIMINALITY IS TRANSMITTED FROM ONE FAMILY MEMBER TO ANOTHER. HOWEVER, SELECTIVE PROSECUTION OF PERSONS FROM FAMILIES IN WHICH SOME MEMBER HAS A CRIMINAL RECORD APPEARS TO BE AN IMPORTANT FACTOR. ANALYSIS OF DATA ON SELF-REPORTED DELINQUENCY AMONG THE TARGET BOYS AT AGES 14-17 AND 18-19 SHOWS THAT, FOR ALL LEVELS OF MISBEHAVIOR, BOYS WHOSE FATHERS HAD CRIMINAL RECORDS WERE SUBSTANTIALLY MORE LIKELY TO BE CONVICTED OF AN OFFENSE THAN WERE OTHER BOYS. SUPPORTING DATA AND A LIST OF REFERENCES ARE INCLUDED. (LKM)