The electrical parameters of both vitelline and plasma membranes have been measured in Marthasterias glacialis oocytes. Voltage-current relationship was studied by an original method using a single intracellular micro-electrode. The analysis of V-I curves obtained by this method reveals rectifying properties of the plasma membrane. Bath application of 1-methyladenine, the hormone wich controls meiosis reinitiation, triggers without lag a partial depolarization of the plasma membrane, whereas the total ionic conductance undergoes typical variations.