OPINION STATEMENT: The activity of a particular esophageal disease, such as eosinophilic esophagitis (EoE) or achalasia, can be evaluated using clinician-reported outcome (ClinRO) measures assessing various endoscopic, histologic, functional, and laboratory findings, and patient-reported outcome (PRO) measures. The patient-reported outcome (PRO) measures are those that are designed to be self-reported by patients. Commonly used PRO instruments include those that assess symptom severity, health-related quality of life, "general" quality of life, or health status. Regulatory authorities increasingly rely on PRO measures to support labeling claims for drug development. Validated PRO measures for various esophageal diseases are needed in order to unify and standardize the way disease activity is assessed, define clinically meaningful endpoints for use in interventional and observational studies, compare the efficacy/effectiveness of various therapies, and optimize therapeutic algorithms for management of these diseases. This article reviews commonly used PRO instruments designed to assess symptom severity and quality of life in adult patients with EoE and achalasia.