In a group of 7 male colony-bred sand rats fed with rat pellet chow ad libitum a mellitus syndrome was developed. When a hyperglycemia was registered the diet was switched to green cabbage ad libitum and again to rat pellet chow after seven weeks of green cabbage treatment. An elevated caloric intake together with a rapid increase of body weight was registered only during the first 5--7 weeks after weaning. The influence of diet treatment on glucose tolerance, insulin immunoreactivity in plasma and glycerol in serum was tested by an intraperitoneal glucose loading. As a reference this test was carried out in the same way in a group of 6 mature sand rats of our colony breeding treated exclusively with green cabbage. Hyperinsulinemia with disturbed glucose tolerance was demonstrated as a transient symptom during the development of the diabetic syndrome. Hyperglycemia was accompanied by a highly disturbed glucose tolerance and a relatively diminished insulin immunoreactivity. In this state the content of glycerol in serum was elevated in the range of one order. Green cabbage treatment lowered the insulin immunoreactivity in plasma to values which were found in sand rats after they had been captured. Moreover, it repaired the glucose tolerance to that in sand rats treated exclusively with green cabbage and lowered the lipolytic activity. It made fit the sand rats to redevelop a hyperinsulinemia in the state of disturbed glucose tolerance during refeeding of rat pellet chow. The interaction of insulin and catabolic hormones in the regulation of glucose homeostasis and lipolytic activity during the development of a diabetic syndrome and the influence of dietary factors are discussed.