To determine the differences in the follicular development process of normal and miniature pigs, we compared the expression of matrix metalloproteinases (MMP) in these two breeds throughout folliculogenesis. In normal pigs, MMP-9 was highly expressed in all stages of the follicular development as well as during ovulation. The follicular development exhibited strong gelatinase activity. The expression of MMP-2 remained insignificant throughout folliculogenesis in both breeds. However, for the follicles of miniature pigs, MMP-2 level was higher than that in normal pigs. Thus MMP types may regulate the remodelling of follicular tissue in the ovaries of normal and miniature pigs. The differential expression of MMPs observed in this study reflected the mechanisms underlying ovarian follicular development in these two breeds.