Various microalgae species have shown a differential ability to biore- mediate atmospheric CO2. This chapter reports biomass concentration, biomass productivity, and CO2 fixation rates of several microalgae and cyanobacteria species under different CO2 concentrations and culture conditions. Research indi- cates that microalgal species of Scenedesmuss obliquss, Duniella tertiolecta, Chlorella vulgaris, Phormidium sp., Amicroscopica negeli, and Chlorococcum littorale are able to bioremediate CO2 more effectively than other species. Fur- thermore, coccolithophorid microalgae such as Chrysotila carterae were also found to effectively bioremediate CO2 into organic biomass and generate inorganic CaCO3 as additional means of removing atmospheric CO2. Important factors to increase the rate of CO2 bioremediation such as initial cell concentration, input CO2 concentration, and aeration rate are reviewed and discussed.