Experiments were carried out to assess Spirulina fusiformis, a blue-green alga, as a source of vitamin A in preschool children. The absorption of total carotenes and β-carotene from a single dose of Spirulina containing 1, 200μg of β-carotene was examined in apparently healthy children aged 3 to 5 years. After stabilization on an almost carotene-free diet taken for 7 days, a bolus dose of Spirulina was fed along with the meal. Fecal excretion of total carotene and β-carotene for 4 days prior to the supplementation and 4 days after supplementation were examined. The effect of daily supplementation of either Spirulina or of vitamin A for one month on serum retinol levels was also examined. The mean absorption of total carotene was found to be 72.3%; and that of β-carotene, 75.2%. Serum retinol showed a significant improvement in both the Spirulina- and vitamin A-supplemented groups, the increase being slightly better in the vitamin A-supplemented group. On withdrawal of the supplements, serum retinol levels returned to presupplementation levels by 1 to 3 months in both groups. The bioavailability of carotenes from Spirulina is thus comparable to that from other sources such as carrots and green leafy vegetables, thus suggesting the potential use of this alga as a dietary source of provitamin A.