Abstract: A dual writing element retractable pen includes coaxial upper and lower barrel members, an upper cylindrical cam part being integrally formed with the upper barrel member and having a bottom cam surface. A matching lower cylindrical cam part telescopes the upper barrel member and is oriented so that the confronting end faces of the cam parts delineate a cam groove having opposite oppositely inclined sections. A rotatable guide member longitudinally slideably supports pen cartridge coupled chucks having followers engaging respective cam groove sections, the guide member being coaxial with the barrel. In one form, the lower cam member is integrally formed with the lower barrel member and, in another form, the lower cam and barrel members are an integrally molded unit and the guide member terminates in an external finger knob.