Fiber-optic evanescent wave Fourier transform infrared spectroscopy (FEW-FTIR) is a new method developed for different applications for surface analysis of materials, including the diagnostics of skin and living tissues. Our technique allows for the detection of inconsistencies in the molecular structure of normal skin surface non-invasively and in vivo . This FEW-FTIR method is direct, non-destructive and fast (seconds). Our optical fibers for the middle infrared (MIR) range are non-toxic, non-hygroscopic, flexible and characterized by extremely low losses. The combination of Fourier transform infrared spectroscopy and advanced fiber technology in the MIR range has opened the door for new powerful diagnostic tools for investigations of many skin surface phenomena, including normal skin, process of aging, allergies and precancerous conditions. Our method could be extended to applications involving the detection of the influence of environmental factors (sun, water, pollution and weather) on the skin surfaces of children and adults. In this study, we have investigated non-invasively more than 118 cases of normal skin in vivo in the range of 1450–1800 cm−1. We compare the FEW-FTIR spectra of palm, hand and elbow tissue. The results of our surface analysis of skin tissue are discussed in terms of structural similarities and differences on a molecular level. Copyright © 1999 John Wiley & Sons, Ltd.