Background: Age-related changes in the elasticity of the human skin have been demonstrated as well as those due to proto ageing. Aims and Methods: To investigate if UV irradiation causes similar changes in the elastic properties of skin, hairless mice (HR/ICR) were irradiated chronically with suberythemal doses of UVA or UVB. Using a recently designed, commercially available noninvasive in vivo instrument, we compared skin thickness and elasticity after 8 weeks of UV exposure with age-matched control mice. Results: Skin thickness increased significantly after UVB irradiation. Skin elasticity (Ur/Uf) decreased significantly after UVA and UVB irradiation, and the ratio of viscosity to elasticity (Uv/Ue) increased significantly after UVA irradiation. Intrinsic immediate strain (Ue*) and intrinsic delayed strain (Uv*) decreased significantly after UVB and UVA exposure. These changes were similar to those reported previously in an in vivo study on human face skin using the same instrument. Conclusion: This finding suggests that the Ue* and Uv* changes observed in human facial skin are associated with actinic ageing caused by chronic UV exposure.