Hyaluronidase from two different strains of Streptococcus agalactiae was purified and characterized. The purification was performed successively by chromatography and rechromatography on phenylsepharose, gel filtration with FPLC on Superdex G 200 and isoelectric focusing. The purified hyaluronidase had an isoelectric point of 8.75 and a molecular weight of approximately 116,000 D. It showed maximal enzyme activity at pH 6.30 and 40 degrees C. The Michaelis constant was estimated to be 8.17 x 10(-2) mg/ml. Hyaluronidase was stimulated only by Mg++ and inhibited by Zn++, Al , Cu++ and Fe++ at a final concentration of 10 mmol/l, respectively. The enzyme splitted hyaluronic acid and in low amounts dermatan sulphate and chondroitin sulphate A. Additionally, synthetic polyanions (like polymers of gentisic acid with formaldehyde and hydroxy sulphonic acid with formaldehyde) turned out to be also potent inhibitors of the enzyme.