Primary care physicians are uniquely positioned to practice primary and secondary cancer prevention. However, despite a positive commitment, many physicians are pessimistic about the success of their interventions. This study describes the self-reported cancer prevention practices and perceived obstacles of 1600 Texas primary care physicians. These practices differed by primary care specialty and by length of time in practice. Time constraints were uniformly perceived as the leading obstacle to the provision of smoking cessation counseling. High cost, lack of third-party reimbursement, and poor patient compliance were cited as the leading barriers to patient referral for screening mammography. Professional education should stress to physicians that interventions need not be elaborate, expensive, or time consuming, the main purpose being to motivate and reinforce patient behavior. The special challenges of introducing health promotion activities into the clinical setting must be addressed with practical aids such as prompting systems, flowsheets, and computer-based aids for monitoring compliance rates.