The electrical resistivity distribution at the base of La Soufri`ere of Guadeloupe lava dome isreconstructed by using transmission electrical resistivity data obtained by injecting an electricalcurrent between two electrodes located on opposite sides of the volcano. Several pairsof injection electrodes are used in order to constitute a data set spanning the whole range ofazimuths, and the electrical potential is measured along a cable covering an angular sector of≈120◦ along the basis of the dome. The data are inverted to performa slice electrical resistivitytomography (SERT) with specific functions implemented in the EIDORS open source packagededicated to electrical impedance tomography applied to medicine and geophysics. The resultingimage shows the presence of highly conductive regions separated by resistive ridges. Theconductive regions correspond to unconsolidated material saturated by hydrothermal fluids.Two of them are associated with partial flank collapses and may represent large reservoirsthat could have played an important role during past eruptive events. The resistive ridges mayrepresent massive andesite and are expected to constitute hydraulic barriers.