Incidence of autoimmune diseases is rising rapidly in the developed world and treatment of such diseases will be a major burden on Government health resources of the future. Whether systemic or organ-specific, immune cell destruction of the target tissue normally requires co-operative interaction of a many distinct immune cells. Detailed knowledge of the cells and signal pathways involved in tissue destruction is paramount to the design of novel therapeutics. Several organ-specific autoimmune diseases e.g. multiple sclerosis, rheumatoid arthritis and type 1 diabetes have long been attributed to T cell-mediated destruction of the target tissue. However, recent reports from both murine models and man have suggested that B cells are principal players in these T cell-mediated diseases. In this review, we discuss the evidence that supports a link between B cells and the autoaggressive T cell response in type 1 diabetes and how accumulating evidence suggests targeting B cells may offer a novel therapeutic strategy for this autoimmune disease.