The New Zealand obese mouse (NZO) is characterised by hereditary obesity and type 2 diabetes, including insulin resistance, hyperinsulinemia and glucose intolerance. This well established diabetes model is reproduced by inbreeding. However the specific symptoms may differ among the individual colonies of NZO mice. The NZO mouse colony kept in Halle was analysed by means of morphological, physiological and biomolecular investigations. The results where compared to those obtained from metabolically unimpaired NMRI (Naval Medical Research Institute) mice and data taken from the literature. The aim of this study was to find specific changes in the β-cells of the islets of Langerhans. The immunofluorescence staining of the islet hormones insulin, glucagon and somatostatin showed a β-cell hyperplasia in connection with modifications of the islet anatomy. Measurements of blood glucose and plasma insulin levels of four different age-groups showed a slightly decreased glucose level and a compensatory, age-related dramatic increase of the plasma insulin concentration. Perifusion analyses uncovered an impaired glucose tolerance of separated islets of neonatal mice. Furthermore, immunostaining of the glucose transporter GLUT2 and investigations of its mRNA expression level were performed. GLUT2, the first component of the glucose-sensing-complex, was not found at the cell surface but in the intracellular compartment of young NZO mice. In senescent NZO mice almost no GLUT2 was detectable. A slightly reduced expression level of Glut2-mRNA was found in NZO and NMRI mice strains, however, the expression level of Glut2-mRNA in the NZO mice decreased significantly with age. A regular nightly increase of melatonin synthesis was confirmed using the HPLC technique after derivatisation. Investigations of the circadian rhythms did not show relevant differences between both mice strains. Our NZO mouse colony is in all typical diabetic features well comparable to other NZO mouse colonies. The findings about the GLUT2 extend the knowledge about NZO mice. Moreover, a basis for following chronoendocrine studies on the diabetic mouse model NZO was established.