The objective of this cross-sectional, retrospective study assessing commercially insured patients was to provide a useful benchmark to US health care payers and decision makers to assess quality of care, medication use and adherence, and health care resource utilization/costs associated with common chronic diseases. Measures of quality of care were suboptimal and substantial numbers of patients were not using any pharmacotherapy considered acceptable according to treatment guidelines. The widespread nature of undertreatment, poor medication adherence, and substantial health care costs highlights deficits and points to the need for comprehensive, multifaceted strategies to improve clinical and economic outcomes for chronic diseases.