Microalgae hold a great potential to serve as feedstocks for biodiesel production. Tropical and subtropical zones have more solar energy than temperate areas for microalgal culturing. However, outdoor high irradiance results in high temperature in the culturing medium, which is damaging if not lethal to most known microalgal species. New microalgae with heat tolerance, high growth rates and high lipid contents are desirable to establish this industry. Four new green microalgae were isolated in southern Taiwan, located in the subtropical zone. All four species are members of the genus Desmodesmus in the family Senedesmaceae. Two of the four species survived at 45¢Jfor 24 hours, with 5 to 13% mortality rates caused by the heat. Lipid contents of two species reached over 50% in dry biomass under nitrogen starvation. Oil accumulation in tion. Oil accumulation in tion. Oil accumulation in tion. Oil accumulation in the four species positively correlates with their photosystem efficiencies during stress treatments (R2=0.90).