This study explored the effects of the major growth parameters for Synechococcus elongatus PCC7942 for the purpose of maximizing cell growth. Preliminary studies in shake flasks revealed that an optimization of components in BG-11 growth medium resulted in no significant improvements for the specific growth rate and biomass concentration. However, an optimal temperature of 33 degrees C and light intensity of 120E/m(2)s provided a maximum specific growth rate of 0.052h(-1) and a maximum biomass concentration of 0.50g/L. Further studies of light intensity, CO2 concentration, and gas flow rate in a 1L airlift photobioreactor showed that air enriched with 5% CO2 with a flow rate of 1L/min, temperature of 33 degrees C, and light intensity of 6E/m(2)s achieved a maximum in biomass concentration of 1.07g/L with a specific growth rate of 0.026h(-1). The specific growth rate and biomass concentration diminished when CO2 concentration and light intensity increased above 5% and 120E/m(2)s, respectively. CO2 absorption experiments also revealed that growth was significantly limited by CO2 when supplied with air, whereas 10% CO2 lowered the pH and consequently reduced the specific growth rate. Application of a 12:12 hour light-dark cycle resulted in a significant drop in biomass growth.