The reliability, construct validity, and discriminant validity of a new self-report questionnaire, the Questionnaire on Stress in Diabetic Patients, were assessed in a sample of 617 patients with insulin-dependent diabetes mellitus and non-insulin-dependent diabetes mellitus. The 90-item inventory is designed to assess psychosocial stress associated with problems in daily living with diabetes. One of the intended uses is to identify psychosocial factors hampering patient compliance with the necessary treatment regimen. Values of Cronbach alpha ranged from 0.63 to 0.88. The results provide initial evidence for the reliability and validity of the instrument.