AbstractTitle. Measuring symptom occurrence and symptom distress: development of the symptom experience indexAim. This paper is a report of a study to assess reliability and construct validity of revised and refined version of the Adapted Symptom Distress Scale: the Symptom Experience Index (SEI).Background. The development of the SEI, a 41‐item Likert Scale assessing 20 symptoms, was based on self‐regulation theory and an integrative conceptual analysis of symptom assessment and management. The model emphasizes the difference between the occurrence of a symptom (or multiple symptoms) and the distress (emotional) response to the occurrence of a symptom. It is the distress from symptom occurrence that promotes a person to take action and use known coping strategies to prevent the symptom occurrence or alleviate the distress from the symptom.Method. A contrast‐group and test‐retest approach was used to assess construct validity and reliability with a convenience sample of 158 patients at United States of America in 2003–2004.Results. The SEI demonstrated reasonable internal consistency with a Cronbach's alpha of 0·91 for symptom experience, 0·85 for symptom occurrence and 0·84 for symptom distress. Test‐retest reliability was supported by high intra‐class correlation coefficients (symptom experiencer = 0·93; symptom occurrencer = 0·94; symptom distress,r = 0·92). Construct validity was supported by statistically significant differences between patients and healthy adults.Conclusion. The SEI can be used as a baseline and outcome measure to assess the impact of multiple symptoms on patients, and the effectiveness of interventions to manage these symptoms.