Physicians provide one source o fin formation about the quality of care in health plans, but concerns exist that physicians cannot distinguish quality from financial considerations or other underlying attitudes. We examined whether physicians can (a) distinguish different domains of health plan quality and (b) distinguish health plan quality from their underlying attitudes. We analyzed data on 419 generalist physicians from four health plans. Three scales assessed physicians' perceptions of facilitators and barriers to high-quality care in the plans and the clinical capabilities of plan physicians. Structural equation modeling indicated that physicians could distinguish domains of health plan quality. Physicians could also distinguish plan quality from their attitudes toward the plan, but plan quality was more highly correlated with general managed care attitudes than expected. These data suggest that physicians can provide information about health plan quality, but it will be important to validate these measures against patient outcomes.