The use of pens in human-computer interaction has been investigated since Ivan Sutherland’s Sketchpad graphical communication system in the early 1960s. We provide an overview of the major developments in pen-based interaction over the last six decades and compare different hardware solutions and pen-tracking techniques. In addition to pen-based interaction with digital devices, we discuss more recent digital pen and paper solutions where pen- and paper-based interaction is augmented with digital information and services. We outline different interface and interaction styles and present various academic as well as commercial application domains where pen-based interaction has been successfully applied. Furthermore, we discuss several issues to be considered when designing pen-based interactions and conclude with an outlook of potential future challenges and directions for pen-based human-computer interaction.