Abstract: Process and apparatus for the manufacture of hollow fibers are disclosed in which at least two layers of molecularly orientable thermoplastic material are together passed through a pressure nip between two rollers, each of which has in its periphery annular grooves with lands therebetween, the grooves in the respective rollers being accurately aligned, whereby the layers are caused to form at least the boundaries of enlarged portions which are connected by thin integral portions or completely severed from each other. Any interconnected enlarged portions are then separated by mechanical means.