Abstract: An electromagnetic piston and cylinder device for producing linear motion has a cylinder provided with a plurality of magnetic devices along its length for producing radial magnetic fields of alternative polarity. The piston is also provided with at least one magnetic member producing a further radial field and there is control means for carrying piston radial field or the cylinder radial fields to alternate whereby to cause relative movement between the piston and cylinder. The piston and cylinder device is preferably sealed but connected to a fluid reservoir whereby the device operates as a combined spring and actuator.