Over-production of gelatinase A (MMP-2) or under-production of its inhibitor (TIMP-2) may result in the matrix degradation crucial for metastasis, and early evaluation of their expression in primary tumor would offer important prognostic informations. RT-PCR amplicons of MMP-2 and TIMP-2 mRNA from tissue biopsies of 13 breast carcinomas and one fibrocystic mastopathy were quantitated. In comparison with their normal-tissue counterparts, their expression trends were not uniform: in some cases MMP-2 increased in the tumor without changes in TIMP-2, in others TIMP-2 expression also increased, although to a lesser extent than MMP-2; only in 2 cases was it slightly lower in the tumor tissue. Nevertheless, clearer insights were gained from the comparison of the ratio (R) between MMP-2tumor/normal and TIMP-2tumor/norma: as in the fibrocystic mastopathy, the R in carcinomas without lymph-node involvement (LN−) was usually lower than 1 in most cases. In contrast, in 5 out of 6 patients with lymph-node metastasis (LN+), the ratio ranged between 2 and 4. While the R magnitude was not related to the frequency of positive lymph nodes out of the total analyzed, nor to relapse status at follow-up (all relapse-free), the clear-cut difference between the LN− and LN+ groups was statistically significant. Results suggest that evaluation of MMP-2/TIMP-2 mRNA balance may constitute an early prognostic approach, which may also be more reliable concerning cancer aggressiveness as compared with the MMP-2 alone, and that boosting TIMP-2 expression may be a therapeutic strategy to prevent metastasis. © 1995 Wiley-Liss, Inc.