Matrix metalloproteinases (MMPs) are thought to play important roles in the gastrulation of Cynops pyrrhogaster embryos. MMP cDNAs were cloned from Cynops pyrrhogaster and we report here a novel MMP called CyMMP, which has strong similarity to MMP-21 (XMMP) in Xenopus. Reverse transcription-polymerase chain reaction (RT-PCR) analysis demonstrated that CyMMP mRNA was already present in cleavage stage embryos. The amount of the mRNA then gradually decreased, but increased again starting in late gastrula. There were regional differences in the level of CyMMP mRNA expression at late gastrula: the involved archenteron roof was the predominant site of expression of the gene, while there was weak expression in the neuroectoderm and epidermal ectoderm. We also found that the gene was activated in artificially mesodermalized ectoderm. The present findings indicate that CyMMP mRNA expression is activated in differentiating mesoderm during gastrulation, suggesting that CyMMP plays a role in gastrulation-related cell movement.