Interferograms show long term subsidence of Kupreanof at < 5 mm/yr. Between 2002 – 2003, > 5 cm of inflation is also observed. The location of the subsidence and inflation sources is the same, and both signals are modelled using a point source at 4 – 6 km depth. The subsidence source may extend to shallower levels (< 3 km depth) and also involve the hydrothermal system above an active magmatic system. The period of inflation is attributed to an intrusion of magma, and subsidence may result from cooling and volatile loss from magma intruded into the reservoir, or a reduction in pore fluid pressure due to cooling and volatile loss from the hydrothermal system.