Prostate epithelial-cell apoptosis occurs in response to androgen deprivation. We have hypothesized that continued regression would require stromal changes. Studying apoptosis kinetics up to the 14th day after castration, we identified successive waves of apoptosis, with a prominent peak on day 11. This peak was associated with caspase-3 activity, nuclear translocation of apoptosis-inducing factor and clusterin expression. The apoptosis peak on day 11 was preceded by increased MMP-2 and MMP-7 activation, and MMP-9 expression on days 9 and 10. Treatment with the matrix metalloproteinases inhibitors doxycyclin, hydrocortisone, or GM6001 caused significant reduction in the apoptosis rate on day 11. The present data demonstrate that prostatic epithelial-cell deletion at the 11th day after castration was induced by focal degradation of the extracellular matrix associated with stromal remodelling.