Objectives: The time to the first antibiotic dose (TFAD) has been adopted as a measure of quality of care in patients with community-acquired pneumonia (CAP) based on two retrospective studies of large Medicare databases. The mechanism by which a difference of a few hours in receiving antibiotics can be deleterious is difficult to understand given the historical data regarding how long it takes for antibiotics to influence outcome. We investigated the factors that predict a prolonged TFAD and their association with mortality.Design: Prospective cohort study.Setting: A large tertiary hospital.Patients: Immunocompetent adults admitted to the hospital with CAP.Results: A total of 451 patients with CAP were studied. A TFAD of > 4 h was associated with increased mortality (p 0.017). Altered mental state (p = 0.001), absence of fever (p = 0.02), absence of hypoxia (p = 0.025), and increasing age (p = 0.038) were significant predictors of a TFAD of > 4 h. After adjusting for these factors, the association between TFAD and mortality was not statistically significant (p = 0.131). Similar findings were observed in patients who were 65 years.Conclusions: A delay in administering antibiotics in patients with CAP is more common in patients who present with an altered mental state or minimal signs of sepsis. TFAD is likely to be a marker of comorbidities driving both an atypical presentation and mortality rather than directly contributing to outcome. Using TFAD as an indicator of quality of care in patients with CAP without significant additional clinical information is potentially misleading as the relationships among TFAD, comorbidities, and outcome are complex.