This book concerns the microbiology and technology of microorganisms used in production of fermented food products. It has been written in fifteen chapters. The first chapters include the general concepts of microbial starter cultures, definitions, their types, significance and uses, ecology, classification, factors affecting the argumentative changes by starter cultures, preparation of starter cultures, maintenance and preservation of starter cultures and inhibition factors of stater cultures. The second part include the utilization of starter cultures in food industry such as cheese making, production of fermented milk products, production of fermented meat products, production of baked products and production of vegetables products.