The goal of the present work is to demonstrate that a bulk, ultra-fine grained microstructure can be obtained by the hydrostatic extrusion process in technical purity 99.5% nickel. Deformation was performed at room temperature to a wire of 3mm in diameter with the total true strain 3.8. Microstructure is characterized by light microscopy, TEM, XRD and mechanical properties. Hydrostatic extrusion was shown to be an effective method of severe plastic deformation which allows to generate ultra-fine grained structure within the deformed material. After cumulative hydrostatic extrusion the yield stress has tripled reaching the maximum of 812MPa with moderate elongation of 13%. A mean subgrain size of 200nm has been observed with a considerable diversity in size of individual grains. For the final passes of hydrostatic extrusion slight decrease of the mechanical properties accompanied with an increase in crystallite sizes is observed. This is explained in terms of the thermal softening processes activated by the heat generated during hydrostatic extrusion.