Structure-activity relationships are described for a series of succinyl hydroxamic acids 4a-o as potent and selective inhibitors of matrix metalloprotease-3 (stromelysin-1). Optimisation of P1' and P3' groups gave compound 4j (MMP-3 IC50 = 5.9nM) which was >140-fold less potent against MMP-1 (IC50 = 51,000nM), MMP-2 (IC50=1790nM), MMP-9 (IC50 = 840 nM) and MMP-14 (IC50 = 1900 nM). (C) 2001 Elsevier Science Ltd. All rights reserved.