This course is proposed to provide an introduction, general characters of actinomycetes, relation of them to bacteria and relation to fungi, nature and occurrence of actinomycetes. Also, this course gives the fundamentals of identification key of actinomycetes as well as providing a conceptual and experimental background about different genera of actinomycetes and their biological activities, antibiotics produced by them (types – isolation – assay – activities – mode of action – development of resistance – immunity to antibiotics and its mechanisms – medical actinomycetes.