This report describes the historical evolution, development, rationale and validation of the Hopkins Symptom Checklist (HSCL), a self-report symptom inventory. The HSCL is comprised of 58 items which are representative of the symptom configurations commonly observed among outpatients. It is scored on five underlying symptom dimensions—sommatization, obsessive-compulsive, interpersonal sensitivity, anxiety and depression—which have been identified in repeated factor analyses. A series of studies have established the factorial invariance of the primary symptom dimensions, and substantial evidence is given in support of their construct validity. Normative data in terms of both discrete symptoms and primary symptom dimensions are presented on 2,500 subjects—1,800 psychiatric outpatients and 700 normals. Indices of pathology reflect both intensity of distress and prevalence of symptoms in the normative samples. Standard indices of scale reliability are presented, and a broad range of criterion-related validity studies, in particular an important series reflecting sensitivity to treatment with psychotherapeutic drugs, are reviewed and discussed.