Abstract: A hydraulic intensifier with a piston and cylinder assembly (1) having a first piston (3) in a chamber (4) of low pressure cylinder and a second piston (7) in a chamber (8) of a high pressure cylinder. The first and second pistons are coupled together and the first piston has a larger cross-sectional area than the second piston. A high pressure output (19) is coupled to the chamber of the high pressure cylinder, there being; means (13) for supplying low pressure hydraulic fluid to the chamber of the low pressure cylinder; an electrically operated directional control valve (11) for controlling the supply of low pressure hydraulic fluid to the chamber of the low pressure cylinder; and electronic means (14) for controlling operation of the directional control valve.