The utilization of good-quality and poor-quality roughages (lucerne hay and oat straw) by red and grey kangaroos, Megaleia rufa and Macropus giganteus, compared with sheep was investigated by means of digestibility trials in individual metabolism cages. On average the kangaroos ate slightly less per unit metabolic body weight than the sheep when fed ad libitum, but the differences were not significant. They digested a similar percentage of lucerne dry matter but digested straw much less well, mainly because of their poor ability to digest crude fibre. When nitrogen intakes were low, with the straw diet, the kangaroos retained nitrogen less well than sheep although the digestibility of the crude protein was similar for kangaroos and sheep. The kangaroos appeared to have relatively low energy and nitrogen requirements, probably because of their low metabolic rate, and their weight losses were similar to sheep on the poor-quality diet despite much lower digestible dry matter intakes per unit metabolic body weight. There were no differences between red and grey kangaroos in dry matter digestibilities, nitrogen metabolism, or rate of passage.