The assimilation of [1,6-14C] citric acid and [1,6-14C] adipic acid by the blue-green alga Anabaena variabilis was studied in the dark and in the light. Citric acid was assimilated in the dark and in the light but adipic acid showed only limited assimilation in the dark. In the light the assimilation of adipic acid did not enhance the growth of the alga at a concentration of 2.85 × 10−8 M. Growth was inhibited at adipic acid concentrations greater than 10−3 M.Analysis of the products of adipic acid metabolism showed the presence of aspartic acid, glutamic acid, leucine, proline, and threonine amongst other unidentified compounds. A mechanism of β-oxidation is proposed.