To 1) determine the frequency of identification of attentional and hyperactivity problems (AHPs) by clinicians, and 2) examine whether minority children or children from less well-educated, lower-income, or lower-functioning families would be more likely to be identified as having AHPs. Prospective cohort study of 22 059 consecutive children 4 to 15 years of age being seen for acute, chronic, and health supervision visits. Practices of 401 pediatric and family practice clinicians in 44 states, Puerto Rico, and 4 Canadian provinces. Parent questionnaires included demographic information and the Pediatric Symptom Checklist. Clinician questionnaires categorized psychosocial problems and addressed how assessment of problems was made. Analyses compared children with newly identified AHPs with those with other newly identified psychosocial problems. Clinicians identified behavior problems in 18.7% of children, with 9.2% of the entire sample identified as having AHPs. Among those with newly assessed AHPs, clinicians identified minority children and those from low-income or poorly functioning families as having AHPs at the same rate as other children. However, even after controlling for symptoms, males were more likely than females (odds ratio, 2.81) to be identified as having AHPs. Older clinicians were significantly more likely to identify children as having AHPs (odds ratio, 2.09). In assessing AHPs, clinicians used standardized tools such as behavioral questionnaires for only 36.9% of children, and Diagnostic and Statistical Manual criteria for 38.3% of children. AHPs are highly prevalent in primary care practice. Clinicians do not appear predisposed to label children from disadvantaged backgrounds as having AHPs. Primary care assessment of AHPs lacks standardization.