Dislocations of the shuffle set were introduced into an Si single crystal by indentation at room temperature. Foil specimens for transmission electron microscope (TEM) observation were fabricated using a focused ion beam ( FIB) apparatus. The foil specimens were heated in the temperature range between room temperature and 800 degrees C in the TEM. The shuffle set of dislocations were transformed into a glide set of dislocations at around 400 degrees C. At higher temperatures, screw dislocations in the glide set were transformed into helices. Contrast experiment and stereomicroscopy revealed that the screw dislocation interacted with interstitials. These interstitials must have been introduced during either FIB fabrication of the TEM specimens or during TEM observation at lower temperatures.