Smetana et al systematically reviewed the literature describing outcomes for single medical conditions among patients who receive care from generalists or specialists. Among 49 eligible studies of diagnoses within the narrow area of the specialist's domain, 24 favored specialty care, 13 found no difference in outcomes, 7 varied by individual outcome, 1 depended on physician experience, and 4 favored generalist care. Selection bias was adequately addressed in 58% of studies that favored specialty care and in 71% of studies that found no difference or favored generalist care (P = .52). The authors found more methodologic flaws among studies that favored specialty care than among those that favored generalist care or found no difference. Studies that favored specialty care were less likely to address these key methodologic factors than those that favored generalist care or found no difference in outcomes.