Pemmican, a dehydrated high-fat, high-protein, carbohydrate-free meat preparation was fed, with and without an isocaloric supplement of sugar, to 10 human subjects undergoing simulated survival in a severely cold environment for 9 days. No ill effects were noted that could not be attributed to caloric restriction, and the performance of the subjects was considered adequate for survival situations involving moderate activity. An isocaloric supplement of 40 grams of sugar increased the fasting blood-sugar levels, decreased the nitrogen balance, and decreased the excretion of ketones. During the 3 days following initiation of the dietary regimen, fasting blood-sugar levels and daily nitrogen balances fell precipitately, while ketone excretion rose. After this, however, the blood.sugar levels rose somewhat and leveled off, the nitrogen balance increased appreciably, and excretion of ketones fell gradually to quite lov1 levels irrespective of the low caloric supplement of sugar. These results have been interpreted to mean that the subjects were becoming adapted to the combination of pemmican and restricted caloric intake.