Cruide either extract and two fractions from the lipid namely fraction A (unsaponifiable) and fraction B (saponifiable) were obtained from a dry sample of Sargassum johnstionii. From these extracts different concentrations viz., 150 mu g, 200 mu g, 250 mu g and 300 mu g of extracts (added to 0.2ml solvent) were made and used per disc to test their efficiency to inhibit the growth of Staphylococcs aureus, S. albus, Bacillus magatherium (gram-positive), Proteus vulgaris, Escherichia coli and Psuedomonas aeruginosa (gram-negative). 250 mu g concentrations showed best antibacterial activity from all the extract. Highest antibacterials activity was exhibited by crude ether extract. Fraction B showed better activity than fraction A. Gram-positive bacteria were more sensitive to fractions as well as crule extracts than gram-negative bacteria. Highest antibacterial activity by crude ether extract was observed against Proteus vulgaris