A geoelectrical survey was conducted in the coastal area of Yunlin Hsien, westcentral Taiwan, for the study of electrostratigraphy as well as seawater intrusion. The direct current resistivity method was used, and forty-six vertical electrical soundings with Schlumberger array were carried out in the study area. The sounding data were interpreted using the 1-D inversion method. The results indicate that the shallow part of the study area can be divided into three electrostratigraphic units. They are designatd, from top to bottom, the A, B and C formations.