We applied our colorimetric PPi determination method [Heinonen, J., Honkasalo, S. and Kukko, E. (1981) Anal. Biochem. 117, 293-300] to bacterial cultures and measured the intracellular concentration of PPi in the batch culture of Escherichia coli. The cells growing in minimal medium contained about 2.5 nmol PPi/mg protein (0.5 mM). There was no extracellular PPi. A similar concentration of PPi was found also in cells growing in minimal medium enriched by amino acid mixture.