Our research investigates the production of the storage lipids, triacylglycerol (TAG), from the green microalgae Chlorella vulgaris in various biochemical environments. C. vulgaris is capable of accumulating up to 40% of its weight as TAGs under stress conditions such as nitrogen deprivation. Many studies demonstrate that stresses such as nutrient limitation or high light intensity increase lipid accumulation in a wide range of microalgae strains [1,2]. C. vulgaris is capable of accumulating up to 40% of its weight as TAGs under nitrogen limitation. Under the Energy Independence and Security Act of 2007, the Renewable Fuel Standard program calls for the blending of at least 36 billion gallons of renewable fuels with transportation fuels by 2022 . Only 40% of this goal is expected to be satisfied by corn-based ethanol, leaving room for the development of other renewable fuels such as biodiesel from microalgae to reach that goal . A recently estimated production cost for microalgal biodiesel, $10/gal, emphasizes the economic importance of studying these photosynthetic organisms . In an effort to better understand the bottlenecks to TAG production in C. vulgaris, the effect of carbon supplementation on lipid productivity was assessed. Carbon was supplied to C. vulgaris suspension cultures in the form of humidified air enriched with 2% CO2 or directly to the media as glucose. Cell density, biomass accumulation and lipid productivity were determined for each of the growth conditions. A GC-MS analysis was performed to quantify and profile the lipids produced.