A method for the effective isolation of functionally intact phycobilisomes from the thermophilic cyanobacterium M. laminosus is presented, using an unconventional high buffer molarity for stabilizing the aggregates and introducing a DNAse treatment of the disrupted cells to obtain sharp banding of the phycobilisomes in the linear sucrose density gradients.The structural integrity of the isolated phycobilisomes is demonstrated by a fluorescence emission maximum at 673 nm of aggregated allophycocyanin and by electron microscopy.Besides C-phycocyanin and allophycocyanin, phycoerythrocyanin is a constituent pigment of the phycobilisomes. These pigments indicated in the absorption spectrum of phycobilisomes with a maximum at 610 nm and two shoulders at 650 and 580 nm, respectively, were characterized by spectral data and isoelectric points.