Biologically active substances were reported from cyanobacteria. Many strains of cyanobacteria (blue green algae) are known to produce intracellular and extracellular secondary metabolites with diverse biological activity such as antibacterial, antifungal, antiviral and antineoplastic properties. In the present study attempt has been made to asses the antibacterial effect of aqueous and methanol extracts of six marine cyanobacteria belonging to the genus Phormidium and Lyngbya isolated from coastal region of Orissa against some Gram positive and Gram negative human pathogenic bacteria following Disc diffusion assay method. The results showed that all the test species of cyanobacteria exhibited antibacterial activity on aqueous and methanolic extracts. However the intensity of antibacterial properties varied among the pathogenic strains of bacteria used for the experimental purpose. Among the six cyanobacterial species the antibacterial effect was found to be significant in Phormidium tenue and Lyngbya maintensiana as compared to other test species. This shows greater biotechnological potential of these two species which needs further studies.