Abstract: Pipes or pipelines for transporting sewage, water, slurries, liquid and gaseous hydrocarbons, and the like are interlined with flexible composite tubular lining material. The lining material is matched to the crosswise dimension of the pipe and is adapted to be insertable thereinto and to fit snugly against the inner wall thereof. The lining material comprises a flexible matrix member having a netlike open-meshed configuration, thereby being adapted to receive into its interstices foamable material adapted to expand outwardly upon foaming, into and about irregularities in the wall surface, and to solidify there. The matrix member preferably is extensible lengthwise, and thus reducible in size crosswise, when under axial tension. When released from axial tension, the matrix member recovers to its previous dimensions, except as it may be confined, as against an inside wall of a pipe or pipeline.