Performance of preventive services is an important indicator of high-quality health care, but many recommended services are not regularly offered in primary care practices. Health risk assessments, counseling, and referral to community-based programs help address risk behaviors, many of which are leading causes of preventable death and disability in the United States. This study examined various influences on the delivery of preventive services designed to address smoking, excessive consumption of alcohol, unhealthy diets, and sedentary lifestyles. More than 300 health care providers in 52 practices nationwide have contributed data to this study. Staff participation in quality improvement enhanced work relationships and also diminished the effect of practice size on the performance of preventive care. The use of nurse practitioners, allied health professionals, clinician reminders, and patient registries were positively associated with care delivery.