Three blue bands with apparent molecular masses of 120, 240-475 and 700 kDa were separated from the phycobilisomes of Arthrospira (Spirulina) maxima by sucrose gradient centrifugation. The heavy fraction (H) exhibited an allophycocyanin type of absorption and fluorescence emission spectra. A combination of reverse phase high precision liquid chromatography and sodium dodecyl sulfate polyacrylamide gel electrophoresis revealed the presence of the alpha and beta subunits of allophycocyanin (α A P and β A P ), the core membrane linker of high molecular mass (L C M ) and the special beta allophycocyanin 17 kDa polypeptide (β A P - 1 7 ). The stoichiometry of the respective components was 8:8:1:1 and the apparent mass of the complex (700 kDa) is consistent with (α A P 3 , β A P 3 ) 4 (α A P 2 , β A P 2 , L C M , β A P - 1 7 ) 2 composition. The medium fraction (M) was the most abundant and rich in phycocyanin. The light fraction (L) contained trimers of phycocyanin and allophycocyanin and was resolved into five peaks by hydroxylapatite chromatography, three of which were of allophycocyanins. These allophycocyanins were characterized as (α A P β A P ) 3 α A P 3 β A P 3 L 8 C and the trimer containing the alpha subunit of allophycocyanin-B (α A P - B α A P 2 β A P 3 L 8 C ). We conclude that the phycobilisomes of A. maxima dissociates into a tricylindrical central core (700 kDa), trimers of allophycocyanin which attach in the front and the back of the tricylindrical central core, and the rod complexes of intermediate size which constitute the outer layer of the phycobilisome and are composed of phycocyanin.