Background: The prevention and relief of suffering in palliative care are critical to the well-being and quality of life of patients and families facing life-threatening diseases. Many tools to assess different issues in health care are available, but few are specifically designed to evaluate suffering, which is essential for its prevention, early management, and treatment. Objective: The purpose of this review was to identify and describe existing instruments developed to assess suffering in palliative care, as well as to comment on their psychometric properties. Methods: A review of articles indexed in MEDLINE, PsycINFO, and SciELO up to June 2011 was conducted. All articles reporting the development, description, or psychometric properties of instruments that assess suffering were included. An assessment of their psychometric quality was performed following a structured checklist. Results: Ten instruments that assess suffering were identified. Their main features and psychometric properties are described in order to facilitate the selection of the appropriate one given each patient's context. Conclusion: By taking into consideration all features of the assessment instruments under review, the evaluation of suffering can be made easier. A wide and ever expanding range of approaches is now available, which facilitates the selection of the suffering-assessment instrument that is best suited to the needs of the specific patient. One of the challenges ahead will be to further analyze the psychometric properties of some existing instruments.