Identification of reliable, reproducible, and precise end points for future studies of hospital-acquired and ventilator-associated pneumonia is of paramount importance for approval of new therapeutic agents. As required by the Code of Federal Regulations 21 CFR 314.126, the methods of assessment of a subject's response (ie, end points) must be well defined and reliable. The study protocol and results should explain the variables measured, the methods of observation, and criteria used to assess response. Meeting these requirements has proven to be problematic in clinical trials for the evaluation of new products for the treatment of hospital-acquired and ventilator-associated pneumonia because of the subjectivity of assessing a clinical response end point. There are multiple issues and caveats to consider when selecting appropriate end points for these trials.