AbstractDanielsson, Å., B. Hellman and I.‐B. Täljedal, Glucose tolerance in the period preceding the appearance of the manifest obese‐hyperglycemic syndrome in mice. Acta physiol. scand. 1968. 72. 81–44.After intraperitoneal glucose injections in suckling mice there was a higher frequency of glucosuria in those animals which later developed the obese‐hyperglycemic syndrome. The experimental design had a particular advantage in screening for the early identification of mice which are homozygous for the obese‐hyperglycemic gene. The observations also suggested that impairment of glucose metabolism represents a primary lesion in the obese‐hyperglycemic syndrome. The hypothesis that the accumulation of fat later in life only reflects an adaptation of the adipose tissue to the high circulating levels of insulin in the obese‐hyperglycemic mice deserves further attention.