The Taupo Volcanic Zone (TVZ) of New Zealand is characterized by intensive geothermal activity and frequent rhyolitic volcanism. Sixteen wideband (0.01--1,800 s) magnetotelluric soundings were measured along a 110 km-long profile approximately perpendicular to the strike of the TVZ. A model obtained from 2D inversion of the soundings shows two near-surface regions of high conductance which correspond to low density volcaniclastic sediments, up to 3 km thick, which infill a sequence of collapse calderas. At deeper levels (approximately 5--10 km) a resistive layer underlies the entire TVZ. Modelling shows other conductive zones occur beneath the TVZ, with the shallowest lying below the central part at a depth of 10--15 km. Given the high heat flux and volcanic history of the TVZ, the high conductivity at depth may indicate the presence of connected melt. At greater depth (20--30 km) the upper mantle beneath the TVZ appears to be anomalously conductive, consistent with observed high seismic attenuation. ¿ 1999 American Geophysical Union