The effects of test “loads” containing 50 gm. glucose (CHO); 50 gm. glucose + 30 gm. protein + 40 gm. fat (CHO + P + F) ; 50 gm. glucose + 30 gm. protein (CHO + P); 50 gm. glucose + 40 gm. fat (CHO + F) on plasma glucose, FFA, insulin, and alpha amino nitrogen have been evaluated in adult-onset diabetics. In comparison with CHO, CHO + P + F results in much lesser elevation of plasma glucose. The effect of CHO + P + F is greater than the sum of the effects of CHO+P and CHO+F. Apparently the CHO+P+F pattern is attributable to relatively or absolutely increased insulin release plus modified glucose and protein absorption. On the basis of theoretical and clinical observations, there appears to be good reason to consider the use of diets containing considerable amounts of protein and fat in adult- and juvenile-onset diabetics.