A comparison of leaf-area index (L) in the postflowering period was made between a single cross maize hybrid in Rhodesia and a winter and a spring wheat variety in England. At the beginning of the period L of the maize was lower than that of the wheat but it remained near its initial value for a relatively long time, whereas L of the wheat decreased rapidly. The proportion of L consisting of sheath was much lower in the maize than in wheat. Grain yield was higher in the maize largely because of its longer period of grain growth. In Rhodesia maize might benefit from a greater L than that recorded in this study. The high yields achieved by maize are partly due to the relatively long life of its leaves.