The new series 'Microbiology Monographs' begins with two volumes on intracellular components in prokaryotes. In this first volume, 'Inclusions in Prokaryotes', the components, labelled inclusions, are defined as discrete bodies resulting from synthesis of a metabolic product. Research on the biosynthesis and reutilization of the accumulated materials is still in progress, and interest in the inclusions is growing. 'Inclusions in Prokaryotes' provides historical background and comprehensive reviews of eight well-known prokaryotic inclusions: sulfur globules, polyphosphate granules and acidicalcisomes, glycogen, polyhydroxyalkonate granules, wax ester and triacylglycerol inclusions, cyanophycin, insecticidal protein crystals, and protein inclusion bodies of recombinant bacteria. In addition, cameos of selected less-studied inclusions are presented to generate renewed and continuing interest.