A magnetically detectable plastic, e.g., polyethylene, polyvinyl, etc., pipe for underground use comprises a hollow tubular plastic pipe having particles of magnetic material embedded in plastic and secured integrally with the wall of the pipe. The magnetic particles are of iron oxide or barium ferrite and of a size, shape, distribution and proportion such that the plastic pipe may be easily detected by magnetic detection apparatus on the surface when the plastic pipe is buried at a selected depth under the ground.