INTRODUCTION: The purpose of this review was to identify and critique validation studies focusing on the Edmonton Symptom Assessment System (ESAS), a commonly used symptom assessment tool for advanced cancer and palliative patients. METHODS: Using a comprehensive literature search, the authors identified and screened 87 publications. Thirteen articles were selected for in-depth review, based on the following inclusion criteria: psychometric studies with a primary focus on the ESAS, 1991--2006 publication dates and peer-reviewed English language publications. RESULTS: Most studies involved cancer patients (n = 11). The ESAS format varied across studies, in terms of scale format, item number, item selection and language. Studies focused on gathering reliability estimates (n = 8), content validity evidence (n = 1), concurrent validity evidence (n = 5), predictive validity evidence (n = 1), and sensitivity and/or specificity (n = 3). None of these studies involved patients' perspectives as a source of validity evidence. DISCUSSION: The use of varying instrument formats and limited psychometric evidence support the need for further ESAS validation studies, including the involvement of patients.