This presentation focuses on characterization of growth and hydrocarbon production from Botryococcus braunii as part of an overall project to develop the tools to migrate the unique metabolic capacity of this organism for the production of C30+ isoprene hydrocarbons to other algae and higher plants. This work compliments our ongoing photobioreactor design work to achieve maximum photon use efficiency at minimum power input for algae growth systems. Utilizing stoichiometrically designed growth medium and semi-continuous growth conditions, we demonstrate growth to cell concentrations greater than 20 grams dry weight per liter and producing more than 1.5 grams dry weight per liter per day. Cell density drops off rapidly at higher dilution rates, but biomass produced stays relatively constant. Under the high light conditions used in this work, there is a very significant increase in aggregate size as the periodic steady-state density drops, and this is reflected in an order-of-magnitude variation in optical density (OD₅₅₀) to dry weight ratio which is problematic for bioreactor monitoring. Strategies and progress on genetically engineering hydrocarbon synthesis pathways into Chlamydomonas reinhardtii will be noted but details will be presented in a poster session. Effects of nitrogen availability on productivity have also been examined. Oil content and composition data will be available shortly.