We examined the relationship between collagen crosslinking techniques and dentinum reinforcement. In the present study, the tensile tests, imbibition test and antienzyme test were performed on collagen films mainly composed of type I collagen after ultraviolet irradiation and immersion in tannic acid and glutaraldehyde. The elastic modulus increased with the reaction time, but reduction of elongation at breaking point and increased stiffness were observed. This tendency was enhanced by ultraviolet irradiation. Tannic acid treatment resulted in slower crosslinking than the other two techniques. Antienzyme activity was markedly increased by treatment with tannic acid and glutaraldehyde.