Freund's complete adjuvant (CFA) and BCG vaccine modulate the development of type 1 diabetes in animal models. In non-obese diabetic mice, CFA and BCG significantly reduced the proportion developing diabetes compared with controls. Histological examination showed that autoimmune disease still developed but had been diverted to become nondestructive. In a preliminary trial in 17 newly diagnosed, type 1 diabetic patients, intracutaneous administration of 0.1 mL of BCG 1 mg/mL led to clinical remission in 11 (65%)--by week 4 in 6. Remission has been sustained in 3 for 6-10 months. No side-effects were reported. A double-blind trial of BCG is warranted.