Matrix metalloproteases are known to play an important role in tumor invasion by mediating degradation of extracellular matrix. In this study, we have investigated the expression of the matrix metalloprotease pump-1 gene (also referred to as MMP-7, Matrilysin) in 44 ovarian tumors (12 low malignant potential tumors, 32 carcinomas) and 10 normal ovaries using quantitative PCR. The PCR product was labelled with 32P and a phosphoimager was used to determine the relative expression of pump-1 compared to an internal control beta-tubulin. mRNA expression levels of pump-1 were significantly elevated in 9 of 12 low malignant potential tumors and 26 of 32 carcinomas. Northern blot hybridization showed that the 1. 1-kb pump-1 transcript was abundant in carcinoma but seldom expressed in normal adult tissues including normal ovary. Immunohistochemical localization of the pump-1 protein confirms its expression by ovarian tumor cells. Our results suggest that pump-1 is frequently overexpressed in ovarian tumors and may contribute to its invasive nature or growth capacity, therefore pump-1 may serve as a useful marker for early detection of disease and/or a target for therapeutic intervention in downregulation of tumor progression.