Autoimmune diseases affect 10% or more of the North American and European populations. In organ-specific autoimmune diseases, an organ is targeted by an aggressive immune response, which can damage and even destroy it. Type 1 diabetes mellitus (T1DM), one such organ-specific autoimmune disease, is because of the destruction of the insulin-secreting beta cells in the islets of Langerhans of the pancreas. T1DM is because of the interaction of genetic and non-genetic factors thought to induce an immune response, which destroys insulin secretory cells over months, even years. We present the orthodox position regarding the cause of autoimmune T1DM but also emphasize where that orthodox is not based on a firm footing. We discuss the nature of the disease and how we can predict it with a degree of certainty and how we are now trying to modulate the disease process. Lessons learned from autoimmune diabetes could be relevant to other autoimmune diseases.