THE SELECTION OF FAMILIES FOR DETAILED STUDY WAS LIMITED TO THOSE WHERE THE PRESENTING CHILD UNDER 5 YEARS OF AGE AND HAD BEEN SUBJECTED TO SEVERE PHYSICAL MALTREATMENT. THE PERIOD 1965-1970 WAS STUDIED RETROSPECTIVELY, AND THE YEAR 1971 WAS ALSO STUDIED TO ALERT PROFESSIONALS TO THE EXTENT AND COMPLEXITY OF THE PROBLEM. CHILDREN ENCOUNTERING SEVERE ABUSE FROM JANUARY 1972 TO 1973 WERE COMPARED WITH CHILDREN FROM THE EARLIER PERIOD. THE EXTENT OF CHILD ABUSE WAS DETERMINED FROM DATA REPORTED BY AND FROM CONTACT WITH MEDICAL AND SOCIAL WELFARE WORKERS. THE RATE OF ABOUT 1 NEW CASE REFERRED PER 1,000 CHILDREN UNDER 4 YEARS OLD PER YEAR, EXTRAPOLATED TO ENGLAND AND WALES AS A WHOLE, WOULD ENTAIL THE REFERRAL OF OVER 3,000 CHILDREN YEARLY. THE PROPORTION OF CHILDREN IN THE RESTROSPECTIVE SERIES WITH BRAIN DAMAGE WAS OVER 40 PERCENT, AND THIS FIGURE IS CONSIDERED RELIABLE. A TOTAL OF 38 CHILDREN WERE SEVERELY ASSAULTED BETWEEN 1965 AND 1971 AND CAME FROM 34 FAMILIES. AN ADDITIONAL 22 CHILDREN WERE SEVERELY ASSAULTED DURING THE 1972-1973 PERIOD. OF THE CHILDREN 80 PERCENT WERE UNDER 1 YEAR OF AGE AT THE ONSET OF SEVERE ABUSE; FOUR DEATHS RESULTED FROM ABUSE. A TOTAL OF 225 SEPARATE INCIDENTS CONSISTING OF ONE OR MORE INJURIES WERE ASCERTAINED AMONG THE 38 CHILDREN, A MEAN OF 5.9 INCIDENTS PER CHILD. TYPES OF INJURIES INCLUDED SKULL AND OTHER FRACTURES, BRAIN DAMAGE, NUTRITIONAL DEPRIVATION, AND EMOTIONAL TRAUMA. MAJOR ASSAULTS TENDED TO OCCUR SOON AFTER MARRIAGE OR THE START OF COHABITATION. THE MEAN AGE OF FEMALE ABUSING PARENTS WAS 25 YEARS, AND THE MEAN AGE OF MALE ABUSING PARENTS WAS 25 YEARS. FAMILIES OF SEVERELY ABUSED CHILDREN ARE DESCRIBED IN RELATION TO FAMILY SIZE, YOUTHFULNESS, SOCIAL CLASS, STABILITY, PSYCHIATRIC AND SOCIAL PATHOLOGY, AND MEDICAL PATHOLOGY. DIFFICULTIES ASSOCIATED WITH THE IDENTIFICATION AND PREVENTION OF CHILD ABUSE AND SOME POSSIBLE DETERMINANTS OF CHILD ABUSE ARE DISCUSSED. SUPPORTING DATA AND REFERENCES ARE PROVIDED. (DEP)