Morphometric analysis of pancreatic islets was performed on BB/W rats, which were divided into moderately diabetic and severely diabetic as well as normoglycemic during four months of observation. In normoglycemic rats, total islet area occupied 1.2% of total pancreatic tissue area with a mean area of 19,000 microns2 per islet. Total pancreatic area was markedly decreased to 22% and 10% in moderately and severely diabetic rats, respectively, compared with that of normoglycemic rats. Mean islet area of moderately and severely diabetic rats decreased to 28% and 25% per islet that of normoglycemic rats, respectively, in which severely diabetic rats showed variable sizes of islets. Concomitant morphometric analysis of renal glomeruli showed decreasing sizes of glomeruli in severely diabetic rats whereas number of glomeruli in renal cortex increased in severely diabetic rats compared with normoglycemic rats. Moderately and severely diabetic states were also studied by IV glucose and insulin tolerance tests in regard to plasma glucose and insulin levels compared with normoglycemic rats. During months of observation severely diabetic rats had their total islet area reduced to 10% that of normoglycemic rats as a result of cell mediated immune destruction of islets. And concomitant reduction of glomeruli may be a part of diabetic glomerulopathy. Yet, diabetic rats were normotensive. The degree of water intake, urine volume, urine glucose, urine protein and albumin was also correlated with the degree of diabetes. This study further provides the feasibility of using diabetic BB/W rats for diabetic conditions and their complications.