Commercial cultivation of autotrophic microalgae for food production dates back to the 1950s. Autotrophic microalgae have also been proposed as a source for lipid-based liquid biofuels. As yet, there is no commercial production of such biofuels and estimated near-term prices are far in excess of fossil fuel prices and prices of biofuels based on terrestrial food oil crops. Future costs of autotrophic microalgal lipid-based biofuels are very uncertain. The energetic return of energy investment in liquid autotrophic microalgal biofuels is below a factor 5, even if optimistic assumptions are made about future technologies. Available studies do not allow for firm estimates of life cycle greenhouse gas emissions of autotrophic microalgal lipid-based biofuels. Apart from greenhouse gases, life cycle pollutant emissions of autotrophic microalgal biodiesel may well be more of an environmental burden than the life cycle pollutant emissions linked to fossil diesel or biofuels based on canola or switchgrass. Whether the prospects for, and performance of, lipid-based biofuels from autotrophic microalgae in the more distant future will much improve appears to be largely dependent on breakthroughs in production technology which may, or may not, occur.