A catheter for mapping and ablating comprises an elongated flexible body having a distal region and at least one lumen extending therethrough. A tip electrode is mounted on the distal region. The tip electrode has an exposed distal region having proximal and distal ends and an isolated region proximal to the exposed distal region. The isolated region has an outer surface provided with an electrically insulating and thermally conductive layer. A second electrode is mounted on the isolated region of the tip electrode. This mapping and ablation electrode arrangement provides discrete recording of electrical signals due to the relatively small exposed distal region while allowing the creating of larger lesions due to the large thermal mass provided by the isolated region.