Electron microscopical and immunohistological findings in small biopsies obtained at surgery from two subjects with longstanding type-I-diabetes [insulin-dependent diabetes mellitus (IDDM)] are described and demonstrated in relation to clinical data. The main findings are the first electron microscopical demonstration of A cells scattered as single cells in the exocrine pancreatic tissue and the detection of intermediate cells of the acinar-A cell type. Intermediate cells have never been reported before in the pancreas of diabetes in man.