Chronic heart failure (CHF) is a costly Medicare expenditure, with approximately 70% of the costs of heart failure care attributable to acute, symptom-related hospitalizations. The most common preventable cause of rehospitalization is nonadherence to the CHF regimen. Theoretic models have been used to study adherence; however, these models are predominantly designed for health behavior interventions (ie, smoking cessation, diet modification, or exercise) and focus less on conceptualizing the work involved in carrying out complex self-care regimens. The purpose of this paper was to present one approach for operationalizing the Trajectory Theory of Chronic Illness to study adherence in patients with heart failure. The trajectory model offers unique opportunities to study adherence, specifically because measurable patient attributes are clearer when evaluated in the context of the work required to adhere over time. Using trajectory theory may allow providers to better understand and facilitate patient adherence to the CHF regimen.