Clinical literature has frequently alluded to the role of psychological stress in diabetic blood glucose fluctuations. Past research in the area has been minimal and inconsistent. Recent methodological and measurement advances have made it possible to more accurately assess the impact of psychological stress on long-term diabetic control. Study 1 of this report found a significant positive correlation between the Hassles Scale and Hemoglobin A1 levels in a group of 59 adult insulin-dependent diabetic patients. Social Supports, Type A behavior, and reported therapeutic compliance neither correlated with hemoglobin A1 nor influenced the Hassles-Hemoglobin A1 relationship. In a separate sample of 123 subjects, Study II revealed that diabetic patients generally perceive stress as a very potent factor in blood glucose control, but that different stressors may have differential effects for different diabetic patients. A factor analysis of these data reveals three different stress dimensions of the perceived stress-blood glucose relationship: fight/flight, passive/ruminative, and positive affect.