We report on the existence of two kinds of matrix metalloproteinases (MMPs), MMP-2 and MMP-9, in human seminal plasma. Partial purification of the proteinases was achieved by two steps, consisting of chromatography on a gel-filtration column and then on a gelatin affinity column. Proteinase activities in the chromatography extracts were shown to hydrolyse a fluorescent substrate specific to MMPs (Dnp-Pro-Leu-Gly-Leu-Trp-Ala-D-Arg-NH2). The proteinases were detected using gelatin-zymography, but were not detected using casein-zymography, and were also inhibited by EDTA, EGTA and o-phenanthroline. Molecular weights of the proteinases were determined by SDS-PAGE, gelatin-zymography and Western blot to be approximately 92, 84, 72, 67, 52 and 45 kDa. Gelatin-zymography showed three major bands of activity at 72, 67 and 52 kDa and minor bands at 92, 84 and 45 kDa. Apart from the two smallest bands, these proteinases were all recognized by the polyclonal antibodies for MMP-2 or MMP-9. These results indicate that two kinds of pro-form and active-form matrix metalloproteinases, MMP-2 and MMP-9, and their degradation products, are present in human seminal plasma.