Methods and systems for determining a condition of a selected region of epithelial tissue and/or an organ in a body as well as to diagnose disease, susceptibility, premalignancy or cancer and measure response to therapy, introduction of a drug and to assess the margins of a tumor or resection. The methods utilize through the tissue or organ electrical measurements with alternating current using one or more surface or internal electrodes and measuring the electrical response using one or more surface electrodes, preferably in combination with one or more electrodes in direct or indirect contact with epithelium comprising the organ or tissue under test. The methods are also useful in combination with DC measurements on the surface of the organ or tissue under test. Measurement of impedance, admittance, electropotential and dielectric properties is particularly useful, particularly as a function of frequency and position on and in the tissue or organ.
