In the mammalian ovary, matrix metalloproteinase-2 (MMP-2) is thought to be involved in the regulated turnover of the extracellular matrix during the process of follicle development, ovulation and regression. Information concerning the role of MMP-2 in the chicken ovary is scarce. The present investigation was undertaken to determine the distribution of MMP-2 mRNA within the laying hen ovary as well as to define whether the expression of MMP-2 mRNA changes during the ovulatory cycle. Expression of MMP-2 mRNA in ovarian compartments was determined by RT-PCR analysis at two stages of the ovulatory cycle, i.e. at 22 h and 3 h before ovulation. MMP-2 mRNA was detected in the ovarian stroma and follicles: white, yellowish, small yellow, the largest preovulatory (F3-F1) and postovulatory (P1-P5). In the wall of preovulatory follicles MMP-2 mRNA was found in the theca and granulosa layers. Within the ovary the relative expression of MMP-2 mRNA depended on follicular size, the layer of the follicular wall, the stage of the ovulatory cycle and the degree of regression in the postovulatory follicles. The results obtained indicate that in the chicken ovary MMP-2 may take part in the extracellular matrix remodelling required for follicle growth, development and regression.