Sixty nine strains of Streptomyces sp. isolated from the sediments of Andaman and Nicobar islands (Bay of Bengal) were screened for their antagonistic property against a number of test cultures (Vibrio sp., Klebsiella sp., Escherichia coli, Shigella sp., Proteus vulgaris, Mycobacterium smegmatis, Staphylococcus albus and Bacillus sp.). Nearly 60% of the streptomycete cultures produced antibacterial compounds active against both Gram positive and Gram negative bacteria. Among the positive cultures three strains inhibited all the test cultures. In addition to the above test cultures marine bacteria (Vibrio sp., Aeromonas spp., Flavobacterium spp., Bacillus sp. and Micrococcus sp.) resistant to few known antibiotics (tetracycline, penicillin, neomycin, kanamycin and gentamycin) were also used. Thirty three streptomycete cultures were found to inhibit one or more marine bacteria tested. The ecological distribution and importance of these antagonistic marine streptomycetes are discussed