Abstract: A tow of filamentary filter material for tobacco smoke which is to be converted into a rod-like filler of a filter rod is conveyed along an elongated path first through a stretching or tensioning zone where the filaments are stretched and the tow is converted into a relatively wide flat web, thereupon along a relaxing portion of the path wherein the tensioning action upon the filaments is reduced, thereupon along a third portion wherein at least one side of the running web is contacted by droplets of an atomized plasticizer, and thereafter along a fourth portion of the path wherein the web is gathered by reducing its width so that it more closely resembles a rod which is thereupon draped into a web of cigarette paper or other suitable wrapping material. A wind tunnel surrounds at least one portion of the path to confine at least one stream of air which is caused to flow in the direction of advancement of the tow. A tunnel can surround the stretching zone, the relaxing and/or the fourth portion of the path.