With the aim of developing a model of experimental diabetes by which spontaneous recovery processes can be investigated, we used a lower (1) and a higher (2) dose of streptozotocin (SZ) to find out the lowest possible dose definitely inducing diabetes in mice through beta cell loss but preventing excessive damage to the endocrine pancreas which would exclude restoration processes. After application of SZ (1) to neonatal mice only male animals showed an overt diabetes in adult life. 70 percent of these mice had recovered 15 weeks after appearance of diabetes. Recovery was indicated by normalization of blood glucose, serum insulin, insulin secretion and biosynthesis of isolated pancreatic islets and a reenhancement of the pancreatic insulin content from lower than 10 to 30 percent of control values. After SZ (2) both sexes became hyperglycaemic, and the recovery rate was lower, but was increased by pregnancy in female mice. By means of this model it will be possible to investigate mechanisms and promoting factors of such restoration processes in more detail.