Abstract: An insulated pipeline having spaced sections of heat-insulating material held between a continuous corrosion-resistant coating on the pipe and an outer protective jacket, thereby to provide a flexible composite which renders the pipeline resistant to mechanical and chemical attack while provided heat insulation for the pipeline in a manner which allows the pipeline to flex, for example during laying. The pipeline is preferably in the form of a continuous protective matrix bonded to the pipe and enveloping individual sections of the heat-insulating material.