Various Spirulina strains were assayed for their productivity of gamma-linolenic acid (gamma Lnn). Spirulina platensis ARM-346 was found to accumulate large amounts of gamma Lnn. Urea as a nitrogen source was found to be most effective giving a yield of 13.5 mg gamma Lnn/g dry cell mass. With increase in temperature the gamma Lnn content was found to increase along with biomass. The optimum temperature for maximum gamma Lnn and biomass production was found to be 35 degrees C. The gamma Lnn content was highest at 0.06% (w/v) NaCl and 0.07% (w/v) K2HPO4. Cells cultivated in the orange region of the electromagnetic spectrum as energy source showed a high content of gamma Lnn, and there was less biomass compared to cells grown in red light. When the culture was left in the dark for various times, after 144 h it contained about 26% more gamma Lnn than in conventionally cultivated cells.