To assess the effects of light intensity and quality on the growth and phycobiliproteins (PBP) accumulation in Nostoc sphaeroides Kutzing (N. sphaeroides). Dry weights, dry matter, protein, chlorophyll and PBP contents were higher under 90 mu mol m(-2) s(-1) than under other intensities (both higher and lower). Phycocyanin and allophycocyanin increased with light intensity while phycoerythrin decreased. Fresh weights, protein and PBP contents increased at the highest rates under blue light. Red light resulted in higher values of dry matter, phycocyanin and chlorophyll a. White light at 90 mu mol m(-2) s(-1) or blue light 30 mu mol m(-2) s(-1) were optimal for the growth and phycobiliprotein accumulation in N. sphaeroides.