For producing a drip irrigation conduit (13) having discrete internally located emitter units (6) bonded at axially spaced apart locations of an internal surface thereof, the irrigation conduit (13) is continuously extruded from an extrusion cross-head (2) at a first outer diameter and a first linear velocity and is drawn off through a calibrator unit (8) to a second and lesser outer diameter at a second linear velocity greater than the first linear velocity, the emitter units (6) being continuously supplied on a carrier member (4) which extends from within the extruder cross-head (2) to the region of an inlet of the calibrator unit (8). Whilst so supported the emitter units (6) are accelerated so as to attain an emitter unit linear velocity substantially equal to said second linear velocity and are displaced at this velocity into contact with the extruded conduit (13) where the latter has substantially attained its second linear velocity and therefore continue to be displaced whilst still supported in contac
