The algae Scenedesmus acutus and Spirulina platensis have been considered for use as a supplementary protein in feed and food. This Institute has developed the technology of production and utilization of such algae. It is essential to demonstrate their safety in view of their public health aspects, the interest of the producers and image of these new sources of foods. Both these algae, when in pure form and administered to rats orally up to the dosage of 800 mg/kg of body weight, did not exert any toxic action. No alterations were found in either body or organ weights in the treated animals. The vital organs showed normal histology. Application of both algae onto the skin of albino rats, up to 2000 mg/kg of body weight, did not elicit any skin allergy. All the animals were normal.