Different growth stages of Ulva lactuca were harvested from different biotopes in the Suez Canal during February through April 2003 and subjected to bioassay to detect substances with biological activity. The total alcoholic extract of algal material was fractionated into light petroleum, chloroform, ethyl acetate, fatty acid methyl esters and unsaponifiable matter. The effect of extracts was more pronounced as antifungal than as antibacterial. Petroleum extract had the more prominent effect on Aspergillus niger. Fatty acid methyl ester had a greater effect on Chrysosporium sp, whereas, unsaponifable acetate extract affected Fusarium sp. Bacillus subtilus was found to be sensitive to all solvent extracts. Ethyl acetate extract affected Staphylococcus aureus. Unsaponifable acetate affected Sarcina lutea. The un-saponifable fraction was analyzed by GLC, GC/MS, and TLC. GLC analysis of fatty acid methyl esters and unsaponifiable fraction revealed the presence of twelve fatty acids, palmitic, oleic and margaric acids represented by 70.34, 20.9 and 2.26%, respectively, while the hydrocarbon C-28 was the major unsaponifiable one (63.76%).