Attention-deficit/hyperactivity disorder (ADHD) is a common childhood disorder often treated by pediatricians or family practice physicians. ADHD knowledge held by treating physicians may be an important predictor in patient outcomes. This study examined ADHD knowledge and common assessment and treatment practices of pediatricians and family practice physicians via a national survey sent to members of the American Academy of Pediatrics and the American Academy of Family Physicians. Mailings included the Knowledge of Attention Deficit Disorders Scale--Revised (KADDS-R) and a demographic/practice questionnaire. Although both physician types reported utilizing assessment and treatment methods consistent with current ADHD practice guidelines, findings suggested that pediatricians had greater ADHD knowledge than did family physicians. Physicians who had completed a behavioral pediatric rotation or training specific to ADHD had greater knowledge than physicians who had not done so. The number of new ADHD evaluations conducted monthly was also related to ADHD knowledge. Implications for future research examining ADHD knowledge, training, and outcomes are discussed.