Using uniformly 32P-labeled Chlorella cells as material, composition of acid-soluble inorganic polyphosphates was studied by paper chromatography and ion-exchange chromatography. 2.By the paper chromatographic analysis it was found that the acid-soluble polyphosphates consisted of highly condensed polyphosphates. Ring-forming tri- and tetrametaphosphates, pyrophosphate and tripolyphosphate were not detected in the acid-soluble fraction of the algal cells. 3.By an ion-exchange chromatography with the use of increasing concentrations of KCl-solution as eluant, it was found that the acid-soluble polyphosphate was a mixture of polyphosphates with a variety of condensation number (n-values). Polyphosphates of the n-values between 3 and 15 were only 20% of the total acid-soluble polyphosphate. The majority of the other polyphospates had greater n-values which was eluted with 0.5–1.0 M KCl.