Two resistivity surveys of the region surrounding the Waiotapu, Waikite, and Reporoa thermal areas were made using a multiple-source bipole-dipole method which can detect resistivity variations to several kilometres depth. The surveys show that low resistivity zones are associated with each area, and the broad pattern of resistivity anomalies is similar to that obtained previously using shallow penetrating Schlumberger arrays. At Reporoa, a large resistivity low, about 3 to 5 km across, is seen in both the Schlumberger array resistivity data and the deeper penetrating bipole-dipole data. This anomaly is similar in magnitude and extent to the resistivity lows found at other geothermal fields in the Taupo Volcanic Zone, suggesting that the Reporoa Field is a significant independent geothermal resource, despite the paucity of surface thermal activity and evidence that some of the thermal water may be an outflow originating at Waiotapu. Bipole-dipole resistivity measurements further north show that the Waiotapu and Waikite thermal areas are encompassed by a thick, widespread, conductive layer. The shallow part of this layer, within a few hundred metres of the surface, is inferred to be a thermal aquifer which is continuous between Waiotapu and Waikite. This suggests that the Waikite thermal waters originate east of Waikite, possibly from a source which also supplies the Waiotapu hydrothermal system. The low resistivities at deeper levels are inferred to be largely caused by a sequence of old (pre-Whakamaru) ignimbrites which are difficult to distinguish from the conductive effects produced by the deep hydrothermal system. Computer modelling of the resistivity distribution on a line through Waiotapu and Waikite supports these interpretations.