The development of type 1 (insulin dependent) diabetes mellitus (IDDM) requires a genetically susceptible host and exposure, early in life, to environmental trigger molecules that induce diabetic autoimmunity to insulin producing islet cells. We previously identified islet cell protein p69 as a candidate autoimmune target in IDDM. Here we describe a human genomic p69 fragment which allowed us to map the gene (ICA1) to chromosome 7p22.