In the present study, we examined the effect of intermittent exposure to hyperbaric oxygen (HBO) on experimentally induced tendon laceration in the right hind limb of 56 male Wistar rats. We compared animals treated by HBO (2 atmospheres absolute [ATA] 100% O(2) x 60 min x once per day) with control animals (without HBO) at 3, 7, 14, and 28 days after wound creation. Histology, and pro-alpha1 (I) mRNA by Northern hybridization, pro-alpha1 (III) mRNA, transforming growth factor-beta1 (TGF-beta1) mRNA by RT-PCR were studied. Our results indicate the use of HBO influences the pro-a1 (I) mRNA expression. The level of pro-alpha1 (I) mRNA was especially increased at 7 14 days after laceration by HBO. These results suggest that intermittent oxygen exposure may play a significant role in collagen synthesis and be beneficial for producing the extracellular matrices in tissue engineering.