The monitoring of outcomes is an essential component in evaluating healthcare, yet in critical illness, outcome assessments can be challenged by several factors. These factors include changing acuity levels, recurrent illness, readmission to hospitals, and patient attrition. Additional issues, particularly for elderly patients, include selecting appropriate outcome measures, overcoming barriers to patient recruitment for research, and using retention measures. This article explores issues in conducting outcomes research in acute care and uses a longitudinal prospective panel research study of elderly patients after critical illness as an example. Strategies are discussed that can be used in elderly subjects to facilitate accurate data collection in acute care outcomes research.