Abstract: The invention relates to apparatus with capacitive electrodes for electrical prospecting in a borehole, the apparatus comprising at least two injection electrodes (16, 18), at least two measurement electrodes (28, 34), and a current generator (22) for applying an electrical current between the two injection electrodes. The current generator (22) delivers alternating current at a frequency of 5 kHz to 100 kHz and at a voltage of less than 1000 volts. At least one of the measurement or injection electrodes (16, 28) is placed in a borehole (12, 14) and presents an outer surface that is cylindrical and electrically conductive. The apparatus further comprises means (24) for measuring the current flowing through said injection electrodes, means (36, 36b) for measuring the potential difference between the measurement electrodes, and means for processing the measured current and potential difference to deduce therefrom the characteristics of the subsoil in which the borehole is situated.