A simple questionnaire was developed to help mothers express concerns about their child's behavior. In the 195 cases studied, the mean number of maternal concerns was 3.5 per child (SD ± 3.2, r = 0 to 17). The questionnaire was simple to administer, easily understood, and required approximately 4 minutes for mothers to answer. It was useful in helping mothers focus on their concerns, for 12 times the number of concerns were revealed over those listed on a blank sheet. Play observations and repeat questionnaires demonstrated mothers' concerns to be justified and consistent. When the questionnaire was not available, physicians failed to discuss 55% of mothers' concerns in a usual Child Health Clinic. However, when mothers' questionnaires were available this figure was significantly lowered to 18%. It took the physician on an average only 1.4 minutes longer for the visit with the questionnaire than without. Seventy-three percent of pediatricians found the maternal questionnaire useful, especially when mothers had an average or higher number of concerns. Such a simple, single-sheet behavior questionnaire is useful for mothers and physicians in the Child Health Clinic, is helpful as a screening device separating those mothers who may need further attention from those who do not, and could make the Child Health Clinic more efficient and perhaps more effective. The questionnaire might also be useful in a private pediatricians's office by enabling a more complete discussion of mothers' concerns to be carried out. This would show mothers that the physician was interested in all aspects of their child's health and in the initial visits could prove helpful in establishing a better mother- doctor relationship.