M-17 Agar media is proposed for the cultivation, detection and enumeration of Iactic streptococci in milk and dairy products. The M-17 media are superior to other comparable culture media for the cultivation of the fastidious species Streptococcus cremoris, Streptococcus diacetilactis and Streptococcus Iactis. It is also suitable for cultivation and maintenance of starter cultures for cheese and yogurt manufacturing. This medium helps in detecting streptococcal mutants which are lactose non-fermenters. M-17 Agar media may also be used for the differentiation of bacteriophages infecting lactic streptococci.