A self-potential survey has been conducted around Waita volcano, Kyushu, Japan. A large negative anomaly, generally interpreted as a surface recharge zone, has been observed at medium altitude. However, combined resistivity and self-potential modeling suggests that this anomaly is not necessarily related to surface recharge but to a high permeability column within the body of the volcano. This column encourages lateral flow, which results in a mixture of meteoric water and hot fluid flowing laterally towards the Takenoyu geothermal system. Such a combined modeling analysis has proved to be a useful technique for imaging subsurface fluid circulations. (C) 2002 CNR. Published by Elsevier Science Ltd. All rights reserved.