Assumptions that psychological attributes are specific to particular diagnoses characterize many investigations of chronically ill patients. We studied 758 patients, each of whom had one of six different chronic illnesses, to determine and compare their scores on the Mental Health Index. Five groups of physically ill patients (with arthritis, diabetes, cancer, renal disease, or dermatologic disorders) did not differ significantly from one another or from the general public, but all had significantly higher scores for psychological status when compared with the sixth group, patients under treatment for depression. There was a significant direct relation between higher mental-health scores and advancing age across all patient populations. Patients with recently diagnosed illness in all groups had poorer mental-health scores than did patients whose illness had been diagnosed more than four months previously. A direct relation between declining physical status and mental-health scores was observed. These results suggest that psychological adaptation among patients with chronic illnesses is remarkably effective and fundamentally independent of specific diagnosis.