OBJECTIVE: We undertook this study to test whether Bacillus Calmette-Guerin (BCG) vaccine preserves beta-cell function and increases the remission rate in children with new-onset type 1 diabetes. RESEARCH DESIGN AND METHODS: This was a randomized double-blind placebo-controlled trial offered to children referred to the Barbara Davis Center for Childhood Diabetes or the Baystate Medical Center with a diagnosis of new-onset type 1 diabetes. There were 94 children aged 5-18 years who received either BCG or saline intradermally within 4 months of onset of symptoms and who were then evaluated at 3-month intervals for 2 years. The primary end point was remission, defined as insulin independence for 4 weeks. Secondary end points were C-peptide levels (fasting and in response to a mixed meal challenge), insulin dose, and HbA1c. RESULTS: Of the patients, 47 were randomized to each arm; 7 in the placebo group and 9 in the BCG group did not complete 1 year of the study and are not included in the analysis. One patient from each group achieved remission. Fasting and stimulated C-peptide levels did not differ by treatment arm but declined in both groups and were lower initially and during the entire 2-year period in younger children. Insulin requirements and HbA1c levels did not differ in the two groups. CONCLUSIONS: Vaccination with BCG at the time of onset of type 1 diabetes does not increase the remission rate or preserve beta-cell function.