OBJECTIVE: To assess the impact of personalized exercise prescription on habitual physical activity and glycemic control in sedentary, insulin treated type 2 diabetes patients during a 2-y intervention period. RESEARCH DESIGN AND METHODS: 74 patients were randomized to the intervention (n=38) or control (n=36) group. The intervention group was stimulated to increase daily physical activity through regular, structured, and personalized exercise prescription by a physical therapist over the 2-y intervention period. RESULTS: Physical activity levels at work or in leisure time were not modulated by the exercise prescription intervention. In accordance, no changes in body composition, glycemic control, medication use or risk factors for cardiovascular disease were observed. CONCLUSIONS: Long-term behavioral intervention programs, providing individualized exercise prescription, are not sufficient to change sedentary behavior and/or improve glycemic control in insulin treated, type 2 diabetes patients.