In the proposed Swedish nuclear fuel repository, intended to be placed some 500 meters down in granitic bedrock, the aquatic conditions will be reducing. In order to investigate the plutonium dissolution properties under near repository conditions Pu(III) was prepared using H2 bubbling in the presence of a platinum wire. The plutonium oxidation state was checked by spectrophotometry and a blue Pu(OH)3 precipitate was produced using deoxygenated NaOH. During drying the precipitate turned brownish and was then put in 0.1 M NaCl in pressure vessels. X-ray powder diffraction (XPD) showed no crystallinity of the precipitate. Solubility experiments were performed in pressure vessels that have an insert of PEEK (polyether-etherketone) and two valves, one for gas application and one with a PEEK tube reaching down into the vessel content for sample withdrawal. A small piece of platinum wire was put in each vessel and 50 bar H2 was applied. The pH was adjusted to range from about 3 to 10. All handling was performed in an inert gas (N2) glove box with active oxygen removal yielding oxygen concentrations of <10 ppm. The results after about one year showed concentrations from 10−8 M to 10−5 M at pH 10 and pH 3 respectively.