Abstract: A method is described for determining biological tissue type based on a complex impedance spectra obtained from a probe with a conducting part adjacent a tissue region of interest, wherein the impedance spectra includes data from a number of frequencies. The method may include: obtaining, from the complex impedance spectra, a first data set representative of impedance modulus values, or equivalent admittance values, at one or more frequencies, obtaining, from the complex impedance spectra, a second data set representative of impedance phase angle values, or equivalent admittance values, at one or more different frequencies, applying a first discrimination criterion to the first data set, applying a second discrimination criterion to the second data set, and thereby determining if the tissue region of interest is a tissue type characterised by the discrimination criteria.