In order to increase stabilities and controlled/sustained released of T4 phages were encapsulated within alginate beads which were then coated with chitosan, polyethylene imine (PEI). Quite high loading capacities (over 90%) were achieved in these pH-sensitive microbeads. Coating with those polycations increased significantly stability both in "simulated gastric fluid'' and bile salts especially in the case of PEI coating. The tests conducted in "simulated intestinal fluid'' demonstrated that phages were released from the beads which were active at basic pH in which the release rates were smaller in case of chitosan. PEI concluded to be a better coating then chitosan.