Batch experiments with Dunaliella tertiolecta and Tetraselmis suecica were performed to investigate alpha-tocopherol (alpha-T) production in time, in order to assess the effect of light availability per cell on the production of this antioxidant. In D. tertiolecta alpha-T content increased during growth, in other words, as the cell density increased and the light availability per cell decreased. In T. suecica the pattern was different: alpha-T content was highest during the exponential phase, decreased significantly during the linear phase and increased again towards the end of the cultivation. Chlorophyll (chl-a) content of T. suecica cells decreased after the exponential phase, instead of the expected increase typically observed in shade-adapted cells, suggesting that the culture was nutrient limited. An experiment with extra nutrients showed that chl-a and alpha-T content increased significantly during both the linear and the stationary phase when compared with values in nutrient-deficient conditions. No correlation between alpha-T and chl-a was observed. Our results indicate that diminished light availability does not limit alpha-T production in D. tertiolecta and T. suecica, opening up the possibility of using high cell density, light-limited cultures for the production of this commercially interesting compound.