Do the findings of Waterer et al5 support their conclusions that TFAD performance measures are “… based on incomplete understanding… ,” and that altered mental status “… is the key factor driving both mortality and prolonged TFAD”? Few would argue that our understanding of pneumonia is complete. However, there are three reasons why these findings do not overturn the support by the Medicare studies2,7–8 for the use of TFAD measures in appropriate populations. First, the study populations differ substantially. The cohort of Waterer et al5 was small, excluded an undisclosed portion of nursing home patients, and garnered most cases and statistical power from patients < 65 years old. Interestingly, since Houck et al2 could detect no timing-mortality association among 2,000 patients aged < 65 years who had been excluded from their main analyses,6 the findings of the two studies are actually consistent for younger patients. Second, the analytic methods differed. Houck et al2 stratified their analysis by prior antibiotic treatment and did not detect any timing-mortality association among the 25% of patients who had been pretreated. The lack of adjustment for prior treatment and inadequate statistical power might account for the failure of Waterer et al5 to detect a significant association among older patients. Third, there is no evidence that altered mental status was an important confounder in the Medicare studies. In the national sample of Houck et al,2 the documentation of altered mental status was similar among patients with TFADs of ≤ 4 h (23.2%) and > 4 h (24.4%; p = 0.11), making substantial confounding unlikely. While published findings2 were adjusted for PSI score, parallel analyses using individual PSI components (including altered mental status) in the model gave equivalent results (Wato Nsa, MD; personal communication; January 19, 2006). Initial stratified analyses ruled out heart failure and shock as major confounders,6 while in recent analyses the association between a 4-h TFAD and the 30-day mortality rate remained (OR, 0.74; p < 0.001) when patients with altered mental status were excluded (Wato Nsa, MD; personal communication; January 19, 2006).