SummaryNeither intra- nor extracellular hyaluronidase was produced by E. histolytica in vitro when amebae were cultured aerobically or anaerobically. No specific hyaluronidase inhibitor was produced by the flora of any strains of ameba cultured in this laboratory. Production of hyaluronidase was not induced when cultures of amebae were seeded with hyaluronate. Amebae, isolated from liver abscesses in hamsters, failed to produce hyaluronidase under the conditions used.