The biological activities of des-octapeptide-insulin, des-AsnA21-des-AlaB30-insulin, des-GlyA1-des-PheB1-insulin and trimethionyl-insulin were studied in vitro and in vivo. In vitro we measured, using the isolated diaphragm of the rat, the disappearance rate of glucose in the incubation medium, the incorporation of glucose into the glycogen of the diaphragm and the apntilipolytic activity in the isolated fat cell model. The incorporation of [U-14C]glucose after intraperitoneal injection into the glycogen of the diaphragm and the fat pad tissue was studied in vivo, as well as the incorporation of 14C from [U-14C]glucose into the lipids of the fat pad tissue of the rat.