Acceleration-stat (A-stat) cultivations in which the dilution rate is continuously changed at a constant acceleration rate, leading to different average light intensities inside the photobioreactor, can supply more information and reduce experimental time compared with chemostat cultivations. The A-stat was used to optimize the biomass and product yield of continuous cultures of the microalgae D. tertiolecta in a flat-panel reactor. In this study, four different accelerations were studied, a pseudo steady state was maintained at acceleration rates of 0.00016 and 0.00029 h-2 and results were similar to those of the chemostat. An increase in the acceleration rate led to an increase in the deviation between results obtained in the A-stat and in the chemostats. We concluded that it is advantageous to use the A-stat instead of chemostats to determine culture characteristics and optimize a specific photobioreactor. The effect of average light intensity inside the photobioreactor on the production of vitamins C and E, lutein, and β-carotene was studied using the A-stat. The highest concentrations of these products were 3.48 ± 0.46, 0.33 ± 0.06, 5.65 ± 0.24, and 2.36 ± 0.38 mg g-1 respectively. These results were obtained at different average light intensities, showing the importance of optimizing each product on light intensity. © 2004 Wiley Periodicals, Inc.