THE CHILD STUDY PROGRAM IS A 4-YEAR LONGITUDINAL STUDY OF THE COGNITIVE DEVELOPMENT OF CHILDREN HOSPITALIZED FOR NONORGANIC FAILURE TO THRIVE (FTT) OR NONACCIDENTAL TRAUMA (NAT). THE RESULTS OF TWO DEVELOPMENTAL EVALUATIONS ON THE FIRST 63 ABUSED CHILDREN, DONE AT THE TIME OF ADMISSION AND 6 MONTHS AFTERWARD, ARE PRESENTED, ALONG WITH THE RESULTS OF THE FIRST 19 NONABUSED (CONTROL) SUBJECTS. THE CONTROL SUBJECTS, MATCHED TO THE EXPERIMENTAL GROUP BY AGE AND SEX, WERE OBTAINED FROM PATIENTS AT THE WELL-CHILD CLINICS OPERATED BY THE DENVER DEPARTMENT OF HEALTH AND HOSPITALS AND WERE CONTROLLED FOR SOCIOECONOMIC STATUS BY VIRTUE OF THE FACT THAT PRIMARILY LOW-INCOME RESIDENTS UTILIZE CLINIC SERVICES. DEMOGRAPHIC DATA PERTAINING TO AGE, SEX, ETHNIC BACKGROUND OF THE CHILD, AND NATURE OF THE ABUSE WERE OBTAINED FROM HOSPITAL CHARTS AND FROM PARENT INTERVIEWS. INFORMATION WAS ALSO COLLECTED ON THE AMOUNT OF PRENATAL CARE THE MOTHER RECEIVED AND WHETHER SHE WANTED TO BREAST-FEED THE INFANT. THE TESTS USED FOR MEASURING DEVELOPMENT WERE EITHER THE BAYLEY SCALES OF INFANT DEVELOPMENT (AGES 2-30 MONTHS), WHICH CONSIST OF A MENTAL SCALE AND A MOTOR SCALE, OR THE MCCARTHY SCALES OF CHILDREN'S ABILITIES (28 AND 1/2 MONTHS TO 8 AND 1/2 YEARS), WHICH COMPRISE VERBAL, PERCEPTUAL-PERFORMANCE QUANTITATIVE, MEMORY, AND MOTOR SCALES. FINDINGS SUGGESTED THAT SEX IS NOT A SIGNIFICANT FACTOR, BUT THAT AGE IS; THE MAJORITY OF ABUSE OCCURS AMONG CHILDREN UNDER 3 YEARS OF AGE. IT WAS ALSO FOUND THAT THERE WAS A MUCH HIGHER PROPORTION OF ANGLOS AND A MUCH LOWER PROPORTION OF CHICANOS WITHIN THE ABUSED POPULATION THAN WAS EXPECTED; CHILDREN WHO FAIL TO THRIVE WERE HOSPITALIZED AT A YOUNGER AGE THAN CHILDREN WHO ARE NONACCIDENTALLY TRAUMATIZED; ABUSED CHILDREN APPEAR TO BE AT A GREATER RISK FOR SCORING LOWER IN MORE AREAS OF COGNITIVE DEVELOPMENT THAN ARE CHILDREN WHO ARE NOT ABUSED, AND CHILDREN WHO FAIL TO THRIVE MAY BE AT GREATER RISK FOR SCORING LOWER ON MEASURES OF COGNITIVE DEVELOPMENT THAN CHILDREN WHO EXPERIENCE NONACCIDENTAL TRAUMA. SUPPORTING STATISTICS AND REFERENCES ARE PROVIDED. (DAS)