This volume arose from a conference of the same title held in March 2007 to celebrate the retirement and 80th birthday of Lars Ljungdahl, a doyen of the field; contributions are therefore provided, as would be expected, by a collection of leading experts. Detailed studies of anaerobic micro-organisms have provided insights into hitherto unrecognised metabolic pathways (of which the Wood-Ljungdahl pathway of acetate formation from CO₂ is an excellent example) and roles of metals (in particular tungsten) in biology, while the biotechnological potential of the anaerobes is becoming increasingly apparent as knowledge and understanding of metabolic processes is consolidated. The chapters are assembled into an authoritative volume presenting a state of the art review of anaerobes, principally but not exclusively bacteria. The emphasis is heavily on phylogeny, physiology, biochemistry/enzymology and energetics; indeed, there are fewer than 10 figures illustrating gene organization and no sequence alignments! Nevertheless, it is made quite clear that molecular analyses are being brought to bear in the study of anaerobes, and that information derived from an increasing number of available genome sequences will now underpin their future exploitation in biofuel production and other areas. As a volume in the Annals of New York Academy of Sciences, this publication will find its way into subscribing institutions, but it should also serve as a valuable stand-alone resource for laboratories specialising in research on anaerobes.