OBJECTIVE: To evaluate the effect of intensive diabetes treatment on patient quality of life assessed by the Diabetes Quality-of-Life Measure, the Symptom Checklist-90R, the Medical Outcome Study 36-Item Short Form Survey, and intercurrent psychosocial events in the Diabetes Control and Complications Trial (DCCT). RESEARCH DESIGN AND METHODS: The DCCT was a 29-center prospective controlled clinical trial that demonstrated the beneficial effect of intensive diabetes treatment on retinopathy, nephropathy, and neuropathy. The 1,441 volunteers with IDDM, aged 13–39 years, were randomly assigned to intensive or conventional diabetes therapy. The volunteers were followed for a mean of 6.5 years (range 3–9 years). Quality-of-life data were collected during annual visits. Of the volunteers, 99% completed the study, and >95% of scheduled tests were completed. RESULTS: All analyses of quality of life, psychiatric symptom indexes, and psychosocial event data showed no differences between intensive and conventional diabetes treatment. CONCLUSION: Under careful treatment conditions, such as those followed in the DCCT, patients undergoing intensive diabetes treatment do not face deterioration in the quality of their lives, even while the rigor of their diabetes care is increased.