Milk composition and yield were measured in the black Bedouin goat during 4 d of dehydration followed by 2 d of rehydration. During this time the goats were exposed to strong solar radiation with no access to shade; all of these conditions occur commonly in the desert. Milk yield, initially similar to that found in the desert, was maintained during the first 2 d of dehydration, fell to 35% of the initial value over the third and fourth days and recovered fully during 2 d of rehydration. As yield fell, milk osmolality, and milk fat and protein concentrations rose. During rehydration all 3 fell once more, but whereas osmolality finished below initial values the concentrations of fat and protein remained higher than before dehydration. The milk remained isosmolar with plasma throughout. Total yields of milk solids and milk water during the whole experimental period were 70 and 67% of normal respectively and normal growth of the young was not disturbed.