The book commences with the fossil record of cyanobacteria, and offers a comprehensive treatment of the antibacterial activity of cyanobacteria, based on extensive research conducted by the author. Moreover, the book highlights various other aspects of biological activity, such as anti-fungal, anti-HIV, proteinase inhibitor, anti-mycobacterial, anti-helmintics, anti-inflammatory, cytotoxic, and anti-cancer characteristics of cyanobacteria. The book is based on nine cyanobacterial species, including Anabaena variabilis, Anabaena fertilissima, Nostoc muscorum, Nostoc punctiforme, Nostoc linckia, Nostoc commune, Spirulina platensis, Westiellopsis prolifica, and Hapalosiphon sp. The monograph provides information on the application of cyanobacteria, and all the experiments are described in simple language with explanatory diagrams. The volume also includes a glossary of technical terms used and a list of more than 200 references and an index at the end for the readers convenience. This book would be useful for research students and teachers in universities and colleges who are studying microbiology, medicine, and pharmaceutical sciences in relation to antibacterial effects. Additionally, it will be beneficial for the pharmaceutical industry for research and development purposes related to drug discovery.