An evaluation of the rheological properties of skin is provided by measuring "in situ" the ability of skin to withstand vertical forces of extension. In physiological conditions the biomechanical parameters are reproducible and related to age, sex, skin thickness and the microarchitecture of the connective tissue studied by scanning electron microscopy. These observations shed some light on the structure-function relationship of the fibrous framework of the connective tissue. Variation in the biomechanical parameters can be used to substantiate clinical diagnosis and to monitor the evolution and the therapy of various diseases of the connective tissue.