This paper contains results of four research projects conducted over a five-year period (1986-1990), to evaluate high yielding perennial bunchgrasses as a renewable energy source. In peninsular Florida, tall bunchgrasses including elephantgrass (Pennisetum purpureum Schum.) and energycane (Saccharum spp.), have produced far greater annual dry biomass (DB) yields than forage and sweet:sorghums (Sorghum bicolor (L.)Moench). In the colder locations in Florida's panhandle and at Auburn, Alabama, adapted elephantgrass and energycane genotypes produced comparable-to-much larger DB yields than the annual sorghums. A long near-linear period of DB accumulation, lasting 140 to 196 days, was responsible for the high yielding ability of the perennial bunchgrasses. However, the daily rate of DB accumulation of the bunchgrasses and the efficiency by which incoming solar energy was converted to chemical energy in plant biomass, were not unlike those of other C-4 grasses during active growth. The biomass of elephantgrass and energycane can be stored easily by ensiling because harvested herbage (before ensiling) has a low buffering capacity. Propagation quality of elephantgrass stems can be improved by applying high rates of fertilization to nursery plants.