Experiments were carried out to assess spirulina fusiformis-a blue green algae as a source of vitamin A in rats. In one experiment, the control rats were fed synthetic vitamin A and the experimental rats spirulina as the sole source of vitamin A. The liver vitamin A concentration of spirulina-fed rats of both sexes was found to be significantly higher than that of the control rats. In another experiment the absorption of carotenes from the solvent extract of spirulina and their availability (vitamin A value) as judged by the levels of vitamin A and carotene in plasma and liver were compared with those of synthetic beta-carotene or vitamin A in male rats. The absorption of beta-carotene from spirulina extract tended to be lower than that of crystalline beta-carotene at doses of 550 and 1100 micrograms of beta-carotene. The difference became insignificant at lower beta-carotene dose of 275 micrograms. Spirulina carotene-fed rats did not show a strict dose related increase in the liver or serum vitamin A concentration. The liver vitamin A storage and plasma levels of vitamin A of spirulina carotene-fed rats was much higher than expected. The results of the two studies reported suggest that the algae spirulina can be a valuable source of vitamin A.