Blood flow distribution and occurrence of intermittent, patchy ischaemia in the renal cortex were investigated in anaesthetized dogs before and during burn shock. Severe or moderate thermal injury was induced by scalding 30% of body surface by 90 degrees C or 70 degrees C hot water. Local blood flow in outer and inner cortex was measured by microspheres and by electrodes recording hydrogen gas washout rates. The haematocrit rose much more in the moderately than in the severely scalded dogs, due to marked haemolysis in the latter group. Cortical blood flow was reduced more after severe than after moderate thermal injury. A significant redistribution of blood flow from outer to inner cortex was not demonstrated. Abrupt shifts in local washout rates were observed in most dogs during shock, but was consistently more frequent in the moderately scalded dogs. Such episodes of patchy intermittent ischaemia were not seen after inhibition of prostaglandin synthesis by indomethacin. Thus, prostaglandins may mediate focal vasoconstriction in the renal cortex during burn shock in dogs.