Ulteastructural changes of chloroplasts and mitochondria in mesophyll cells of sugar cane leaves under water stress were described.The outer membranes of the chloroplasts were broken.Many osmiophilic globules were found and the disapppearance.of grana and disruption of lamellae were observed wighin the chloroplasts.The outer membranes of the mitochondria were also broken.The cristae disappeared ?and some lipid droplets in the cytoplasm were observed.The degree of organelles disruption was lighter in the variety Co331 than in the variety Yue Tang 57/423.