We compared parent-reported problems and competencies for national samples of 2,600 4-16-year-olds assessed at intake into mental health services and 2,600 demographically matched nonreferred children assessed in a home interview survey. Parents responded to the ACQ Behavior Checklist, which includes 23 competence items, three competence scales, 216 problem items, eight syndrome scales, Internalizing, Externalizing, and total competence and problem scores. Most items and scales discriminated significantly (p less than .01) between referred and nonreferred samples. There were important sex and age differences in problem patterns, but regional and ethnic differences were minimal. Somewhat more problems and fewer competencies were reported for lower- than upper-socioeconomic-status children. Referral rates were similar in the most urban and rural areas, but they were significantly higher in areas of intermediate urbanization. Correlations of problem scores with those obtained 10 years earlier in a regional survey and with surveys in other countries showed considerable consistency in the rank order of prevalence rates among specific problems. Apparently owing to its more differentiated response scales, the ACQ was susceptible to respondent characteristics that reduced its discriminative power below that of the Child Behavior Checklist. Comparisons of procedures for discriminating between the normal and the clinical range supported the value of a borderline category for children who are neither clearly normal nor clearly deviant. Interview data from the survey sample yielded significantly higher ACQ problem scores for children who had fewer related adults in their homes, those who had more unrelated adults in their homes, those whose biological parents were unmarried, separated, or divorced, those whose families received public assistance, and those whose household or family members had received mental health services. Children who scored higher on Externalizing than Internalizing problems tended to have unmarried, separated, or divorced parents and to come from families receiving public assistance. However, among children whose household or family members had received mental health services, there were greater proportions of both Externalizing and Internalizing patterns than among other children.