The monographs which follow are the result of a process of consultation within the Working Party on Culture Media (WPCM), often extending over several years. Each was prepared as a Draft document by an expert on the particular medium or organism, often the original author. This draft was circulated to interested parties, whose comments were considered by the WPCM. The resulting text was then published as a Proposed monograph and workers were encouraged to assess its functionality and report their comments. When a meeting of the WPCM was satisfied that the monograph was fit for purpose it was given Approved status. Since meetings of the WPCM are infrequent it was thought desirable that certain draft monographs be published in this book before the process of approval commenced. In the pages that follow these are noted as Provisional. It is intended that they will, in due course, be subject to the same consideration as the other monographs. A statement on the formal system of approval for monographs, together with the rationale for the choice of test strains, can be found in Curtis et al. (1998).