In a cross-sectional observational study of Rochester (New York) primary care physicians (PCPs) enrolled in a pay-for-performance (P4P) collaboration, the authors investigated attitudinal factors associated with provider adherence to evidence-based clinical guidelines targeted by explicit incentives. The multivariable adherence model linked guideline adherence rates to provider attitudes among 186 survey respondents, adjusting for individual, practice, and community characteristics. Adherence was defined as the percentage of expected services that were delivered. Attitudes associated with adherence, independent of specialty and prior behavior, were financial salience (adjusted odds ratio [OR] = 3.6; 95% confidence interval [CI] = 1.7-8.4), peer cooperation (OR = 2.0; 95% CI = 1.0-4.0), control (OR = 0.5; 95% CI = 0.3-1.0), and autonomy regarding the health plan (OR = 0.3; 95% CI = 0.1-0.6). The most adherent providers perceived P4P as financially salient and felt supported by peers. Some PCPs might have perceived P4P and external interventions as challenging their autonomy and "crowding out" their intrinsic motivation, leading them to reduce efforts aimed at guideline adherence.