Abstract: In a method for spectroscopic examination of a biological tissue the tissue is irradiated with light having an intensity l.sub.0 (.lambda.) with the wavelength .lambda. being varied, a transmission or reflection spectrum l(.lambda.) is obtained by measuring the intensity of the radiation transmitted or reflected by the tissue dependent on the wavelength .lambda., and an approximate description of the measured transmission or reflection spectrum l(.lambda.) or of the spectrum l(.lambda.)/l.sub.0 (.lambda.) normalized to the incident radiation intensity, or of the quantity log {l(.lambda.)/l.sub.0 (.lambda.)} with an analytical function is made. The analytical function has a Beer-Lambert dependency on a first parameter which describes the absorption properties of the tissue and has a second parameter which is the average path length L(.lambda.) of the photons in the tissue, representing a slice thickness. The first parameter is dependent on concentrations c.sub.