Five cyanobacterial symbionts from Azolla filiculoides, two symbionts from Az. microphylla and two free-living cyanobacteria Nos toe muscorum and Anabaena variabilis were analyzed for chlorophyll (Chi) a, carotenoids and phycobiliprotein contents, heterocyst frequency and nitrogenase activity. The symbiont AS-S1 as well as the free-living N. muscorum and An. variabilis contained highest amounts of Chi a and lowest amounts of carotenoids. The C-phycocyanin content was always higher than that of allo-phycocyanin and C-phycoerythrin. Among the symbionts, AS-S1 contained the highest amount of C-phycocyanin and highest nitrogenase activity. Heterocysts were more abundant in An. azollae than in free-living cyanobacteria.