OBJECTIVE: To determine variables associated with glycemic and body weight responses when adding exenatide to basal insulin-treated type 2 diabetes. RESEARCH DESIGN AND METHODS: Exploratory subgroup analyses based on baseline A1C, disease duration, and BMI of a 30-week study comparing exenatide twice daily to placebo, added to optimized insulin glargine (intent-to-treat analysis: 137 exenatide; 122 placebo). RESULTS: Exenatide participants had greater A1C reductions compared with optimized insulin glargine alone, irrespective of baseline A1C (P < 0.001). Exenatide participants with longer diabetes duration and those with lower BMI had greater A1C reductions (P < 0.01). Exenatide participants lost more weight, regardless of baseline A1C or BMI (P < 0.05). Exenatide participants with longer diabetes duration lost the most weight (P < 0.001). CONCLUSIONS: Exenatide added to optimized basal insulin was associated with improved glycemic control and weight loss, irrespective of baseline A1C, diabetes duration, and BMI. Changes were evident in modestly obese patients and in those with longer diabetes duration.