Usability evaluation of any system helps to identify usability problems to improve system design as well as user interaction. Many usability studies for haptic systems have been conducted but no effort is done to collect usability problems reported in these studies. This paper is an attempt to collect these usability problems to provide better insight of these studies. It classifies these problems in terms of usability factors and tasks. This study may help researchers to propose usability measures for the effective evaluation of haptic systems. © 2011 IEEE.