There are provided magnetic and non-magnetic agarose and agar polyaldehyde beads with diameters ranging from 40 microns up to 1 cm, and processes for the synthesis of such beads. The polyaldehyde compounds e.g. polyacrolein, polymethacrolein or polyglutaraldehyde, were used as microspheres or as powders. The agarose-polyaldehyde beads are capable of covalently binding in a single step, through their aldehyde groups, compounds containing primary amino groups of thiol groups, such as proteins, antibodies, enzymes and drugs. The beads are useful for various biological applications e.g. affinity chromatography, hemoperfusion, ion exchange resins, cell labeling, diagnostic purposes and cell separation.