An FT-IR spectroscopic method was developed for the simultaneous quantitative analysis of biomacromolecular components in biomass, originating from various microbiological sources. For the determination of protein, lipid and carbohydrate content, creatine phosphokinase, egg phosphatidyl choline and starch hydrolysate were chosen as external standards. This selection was based on spectral similarity and case of availability. Protein content was based on the area under the amide 11 band profile around 1,545 cm(-1). Because of the heterogeneous lipid composition in the different species, lipid content was determined using integration over the C-H stretching vibrational Population between 2,984 and 2,780 cm(-1). Carbohydrate content was determined using integration over a C-O and C-O-C stretching band area between 1, 180 and 1,133 cm(-1). Linear regression analysis provided three calibration lines, according to which biomasses from ten species were analyzed. This approach showed good intra-batch reproducibility. With this method we could demonstrate good reproducibility between batches of the same species with similar growth conditions while large differences in biomass composition were observed between the various species. Protein content as determined by FT-IR spectroscopy compared well with the results obtained from elemental analysis.