OBJECTIVE To investigate the effect of flexible intensive insulin therapy (FIIT) and an automated bolus calculator (ABC) in a Danish type 1 diabetes population treated with multiple daily injections. Furthermore, to test the feasibility of teaching FIIT in a 3-h structured course. RESEARCH DESIGN AND METHODS The BolusCal Study was a 16-week randomized, controlled, open-label, three-arm parallel, clinical study of 51 adults with type 1 diabetes. Patients aged 18-65 years in poor metabolic control (HbA(1c) 8.0-10.5%) were randomized to the Control (n = 8), CarbCount (n = 21), or CarbCountABC (n = 22) arm. During a 3-h group teaching, the Control arm received FIIT education excluding carbohydrate counting. CarbCount patients were taught FIIT and how to count carbohydrates. CarbCountABC group teaching included FIIT and carbohydrate counting and patients were provided with an ABC. RESULTS At 16 weeks, the within-group change in HbA(1c) was -0.1% (95% CI -1.0 to 0.7%; P = 0.730) in the Control arm, -0.8% (-1.3 to -0.3%; P = 0.002) in the CarbCount arm, and -0.7% (-1.0 to -0.4%; P < 0.0001) in the CarbCountABC arm. The difference in change in HbA(1c) between CarbCount and CarbCountABC was insignificant. Adjusting for baseline HbA(1c) in a regression model, the relative change in HbA(1c) was -0.6% (-1.2 to 0.1%; P = 0.082) in CarbCount and -0.8% (-1.4 to -0.1%; P = 0.017) in CarbCountABC. Treatment satisfaction measured by the Diabetes Treatment Satisfaction Questionnaire (status version) improved in all study arms, but the improvement was significantly greater in CarbCountABC. CONCLUSIONS FIIT and carbohydrate counting were successfully taught in 3 h and improved metabolic control and treatment satisfaction. Concurrent use of an ABC improved treatment satisfaction further.