In many biotechnological processes, living microorganisms are used as biocatalysts. Biochemical engineering science is becoming more aware that individual cells of an organism in a process can be fairly inhomogeneous regarding their properties and physiological status. Raman microspectroscopy is a novel approach to characterize such differentiated populations. Cells of the anaerobic bacterium Clostridium beijerinckii were dried on transparent support surfaces. The laser beam of a confocal Raman microscope was focused on individual cells viewed through the objective. Single bacterial cells in size approximately 1 microm and sample mass approximately 1 pg could be analyzed within a few minutes, when placed on a calcium fluoride support and using excitation at 632.8 nm. Spectral features could be attributed to all major cell components. Cells from a morphologically differentiated culture sample showed different compositions, indicating the presence of subpopulations. As a reference, the storage polymer granulose was detected. The multidimensional information in Raman spectra gives a global view on all major components of the cell at once, complementing other more specific information-rich methods for single-cell analysis. The method can be used, for example, to study heterogeneities in a microbial population.