Thirteen species of matured marine algae, collected from the intertidal regions around Mandapam, Okha and Malvan Coasts, were extracted with chloroform- methanol and the extracts were subjected in microbial screening for antibacterial and antifungal activities. Most of the extracts inhibited the growth of Escherichia coli, Bacillus subitilis  and Candida albicans. The extract from  Chnoospora fastigiata  showed pronounced antifungal activity against Saccharomyces cerevesciae  and Candida albicans,  whereas Entermorpha flexuosa  exhibited marked activity against E.coli. The Minimum Inhibitory Concentration (MIC) in µg/ml was determined in each case.