Protease activities were detected in quiescent and germinating spores of the ostrich fern (Matteuccia struthiopteris [L.] Todaro). Peak endopeptidase, aminopeptidase, and carboxypeptidase activities were detected 12 to 24 hours after spores began imbibing under light. There was a correlation between activities of proteases, the onset of a decline in levels of soluble protein, and an increase in levels of free amino acids. The earliest visible event of spore germination, breakage of the spore coat and protrusion of a rhizoid cell, was observed after peak protease activity, 48 to 72 hours after the start of imbibition. Results of this study demonstrate similarities in the pattern of protease activities during germination of ostrich fern spores to those of some seeds.