A simple, inexpensive, adaptable system for growing autotrophs has been developed. The culture vessel was made up of a polypropylene bag which could hold 20-40 litres of medium. The cyanobacterial biomass produced by this bioreactor was comparable to that from large volume, open-air systems. The unique advantage in using the bioreactor was the ability to produce contamination-free cultures at an affordable cost. Experiements with various diameters (30, 45, 60 and 70 cm) of photobioreactor showed that column height and diameter of culture vessel played an important role in biomass production of photoautotrophic organisms.