In the present study, the effects of various inorganic nitrogen sources, light intensities, aeration rates and especially vitamins were investigated in vegetative Haematococcus pluvialis Flotow cultures. The best growth among the nitrogen sources was achieved in NaNO(3) (1.0 g/L) and KNO(3) (0.5 g/L) with cell densities of 25.3 and 26.3x10(4) cells/ml respectively. In vitamin trials, the highest cell numbers were found in 0.1(0.3 mu M), 1.0 (4 mu M) and 0.1 ing/L (0.75 mu M) concentrations for thiamin, biotin and B12 respectively. It was also seen that the use of thiamin alone was sufficient instead of using the vitamin mix. Cell growth was significantly higher in 75 and 150 mu mol photon m(-2) s(-1) illuminations compared to 20 and 40 mu mol photon m(-2) s(-1). As for aeration, optimum airflow rate was 1.0 lpm, while supra-optimum levels ceased the growth, cell diameter and pigment content increased. So, it may play a role as a secondary stress factor on H. pluvialis cells in reddening stage.