The purpose of this study was to evaluate the cross-sectional relationship between physician knowledge of hypertension guidelines and blood pressure (BP) control. The authors evaluated a sample of primary care faculty (n=32) and a sample of their patients (n=613). When treating patients as independent observations, the authors found an inverse relationship (r=-0.524; p=0.002) where higher knowledge scores were associated with lower BP control. The authors conducted a multivariate analysis to accommodate the nonindependence due to random physician effects and found that there was no longer a significant association between knowledge and BP control, but there was still a trend (odds ratio=0.84; p=0.130). This study demonstrates that there is no evidence that high knowledge of hypertension guidelines will improve BP control rates and that higher knowledge may actually be associated with lower BP control. Strategies that are designed only to improve knowledge of hypertension guidelines are insufficient to improve BP control rates.