Dry matter production plant water potential, leaf diffusive resistance root system development and water use were studied in selected tropical grasses during a three month dry season. During the first six weeks of the dry season, dry matter production was greater in species which conserved soil moisture during the late wet season. During the second six weeks of the dry season, dry matter production was greater in species which maintained low abaxial leaf diffusive resistance and in which diffusive resistance was relatively insensitive to plant water potential. Rooting density to 120 cm was not related to dry matter production. Dry matter production during both the wet and dry seasons was closely correlated with transpiration as estimated with a soil water balance model.