1. A consistent in vitro effect of anti-insulin serum on glucose metabolism in isolated rat adipose tissue has been demonstrated.
2. Anti-insulin serum added in vitro to epididymal fat pads caused an average decrease in the C-14-O2 formation from glucose-1-C-14 of over 50 per cent, whereas it reduced the incorporation of glucose-U-C-14 into lipids by about 20 per cent.
3. Epididymal fat pads pretreated in vitro with antiinsulin serum oxidized glucose-1-C-14 at a reduced rate compared to control fat pads preincubated in buffer; in the presence of added insulin, however, glucose oxidation was the same in the control and anti-insulin treated fat pads.