Haptic augmented reality (AR) allows a user to explore a real environment augmented with virtual haptic stimuli. For example, medical students can palpate a virtual tumor inside a real mannequin using a haptic AR system to practice cancer screening. To realize such functionality of haptic AR, we need to alter the haptic attributes of a real object by means of virtual haptic feedback. Our research for haptic AR aims at developing a systematic methodology for modulating the haptic properties of a real object with the aid of a haptic interface.