BACKGROUND: Baseline characteristics from the adult cohort of a randomized controlled trial comparing sensor-augmented pump (SAP) and multiple daily injection (MDI) therapy were analyzed for significant relationships with -0.5% A1C change at 1 year of therapy without incidence of severe hypoglycemia (defined as A1C benefit). METHODS: Baseline characteristics were compared with A1C benefit. Statistically significant predictors were analyzed further to determine appropriate cutpoints of relative A1C benefit. RESULTS: Baseline A1C >/=9.1%, age at randomization >/=36 years, and age at diabetes diagnosis of >/=17 years were associated with a greater SAP benefit relative to MDI than other cutpoints. CONCLUSIONS: People with type 1 diabetes who had a high A1C and who were older at diagnosis and older at randomization experienced the most benefit from SAP therapy.