Abstract: A method and a device for lining existing pipelines such as water conduits and sewers disposed in the ground with a flexible hose containing a curable plastic material which hose is introduced into the pipeline to be lined in uncured state and is then made stable in form by curing of the curable plastic material included in the hose. To make possible a rapid and efficient curing of the plastic material included in the hose (4) the hose (4), after being pressed out against the pipeline (1) by means of compressed air, is exposed to radiation energy from a curing aggregate (18) containing a radiation source (19), which aggregate is drawn internally through the hose (4) at the same time as air flows through said hose.