The prognostic staging of cancer in general, and lung cancer in particular, has customarily depended mainly on morphologic distinctions. The gross anatomic extensiveness of cancers is cited with TNM stages that describe the primary tumor (T), spread to regional lymph nodes (N), and metastatic dissemination (M) to distant sites. Microscopic characteristics are cited according to the cancer's cell type (e.g., adenocarcinoma, epidermoid carcinoma) and/or grade of differentiation (e.g., well differentiated, poorly differentiated, anaplastic). Although the clinical manifestations, functional effects, and associated co-morbidity of a cancer are universally recognized as having major prognostic importance, they have not been classified with a standard system of taxonomy. When considered at all, clinical phenomena have been cited with a surrogate index of "performance status" that ignores the underlying clinical dysfunctions while being greatly affected by non-clinical phenomena, such as the patient's psychic status, economic motivations, and system of social support. The current research was done to develop a standard system of taxonomy (or "staging") for the prognostic impact of clinical distinctions in patients with primary lung cancer. Appropriate data were obtained, computer-coded, and analyzed from medical records for the complete clinical course of an inception cohort of 1266 patients who were first treated at either the Yale-New Haven Hospital or the West Haven Veterans Administration Hospital during the interval January 1, 1953-December 31, 1964. The information under analysis included clinical phenomena as well as anatomic extensiveness (TNM stage), microscopic histology, the chronometric duration of the interval from the first symptom of lung cancer to zero time, the iatrotropic reason why the patient sought medical attention, the presence of anemia, the amount of customary cigarette use, and the conventional demographic data for age and gender. The main clinical phenomena were expressed in variables for symptom pattern severity, and co-morbidity. Symptom pattern referred to the existence of specific pulmonic symptoms (e.g., hemoptysis), systemic symptoms (e.g., complaint of weight loss), and metastatic symptoms that might be mediastinal (e.g., superior vena cava syndrome), regional (e.g., the Horner syndrome), or distantly metastatic (e.g., central nervous system). The symptom severity variable included the amount of weight loss, and the existence of severe dyspnea or particularly severe tumor effects (such as mental obtundation, rather than hemiparesis in patients with CNS metastasis). Prognostic co-morbidity was cited for coexisting diseases, such as recurrent myocardial infarctions, that might be more lethal than the lung cancer itself.(ABSTRACT TRUNCATED AT 400 WORDS)