Five algal species forming blooms at North Delta-Egypt, collected from diverse locations, were screened for their efficiency as antibiotic activity against some plant pathogenic fungi. The algal extracts (aqueous and alcoholic) as well as culture filtrate of Spirulina maxima, Oscillatoria agardhii, Chlorella vulgaris, Ulva lactuca and Cladophora albida were tested against a representative group of fungi. Growth inhibition of the fungal species was detected on exposure to each treatment of the algal species. The results show that O. agardhii was the most potent alga with an average growth inhibition of about 49.0 % over all treatments and all tested fungi. The most effective treatment for S. maxima, O. agardhii and U. lactuca was the culture filtrate; meanwhile, the ethanolic extract of both C. vulgaris and C. albida was the most pronounced treatment over all tested fungi. Complete inhibition was observed to Sclerotium rolfsii, Sclertinia sclerotiorum and Verticillium alboatrum on exposure to the culture filtrate of O. agardhii. The results are discussed in the light of the ability of these algae to produce bioactive secondary metabolites, secreted into the surrounded medium, which possess an inhibitory effect on the fungal growth.