Sorghum (Sorghum bicolor [L.] Moench) is the fifth most economically important cereal grown worldwide and is a source of food, feed, fiber and fuel. Sorghum, a C4 grass and a close relative to sugarcane, is adapted to hot, dry adverse environments and this plant is a potentially important bioenergy crop for Texas. The diversity of the twelve high biomass sorghum genotypes was analyzed using 50 simple sequence repeats (SSR) markers with genome coverage. The accumulation of biomass during sorghum development was studied in BTx623, an elite grain sorghum genotype. Genetic similarity analysis showed that the twelve high biomass genotypes were quite diverse and different from most current grain sorghum genotypes. The ratio of leaf/stem biomass accumulation was higher early in the vegetative phase during rapid canopy development and lower later in this phase when stem growth rate increased. This resulted in an increasing ratio of stem to leaf dry weight during development. Numerous cellulose sythase genes have been putatively identified in the sorghum genome. The relative level of Ces5 RNA in leaves decreased during vegetative phase of development by ~32 fold. There was no change in the relative abundance of Ces5 RNA in stems. Also there was no change in the relative abundance of Ces3 RNA in either stem or leaves during the vegetative stage. The knowledge gained in this study may contribute to the development of sorghum bioenergy hybrids that accumulate more biomass and that are modified in composition to make them more amenable to biofuels production.