Pay-for-performance (P4P) has been widely adopted, but it remains unclear how providers are responding and whether results are meeting expectations. Physician organizations involved in the California Integrated Healthcare Association's (IHA) P4P program reported having increased physician-level performance feedback and accountability, speeded up information technology adoption, and sharpened their organizational focus and support for improvement in response to P4P; however, after three years of investment, these changes had not translated into breakthrough quality improvements. Continued monitoring is required to determine whether early investments made by physician organizations provide a basis for greater improvements in the future.