The codes developed or being developed for internal dose assessment were reviewed. Firstly, the current research and development in ORNL were introduced based on the lecture of M. CRISTY in the meeting on April 4 in 1991 at NIRS. Secondly, the typical codes developed in Japan were described mainly on the characteristic aspects. Lastly, three codes in other countries were selected for notable codes having different features. Particularly, the code of LUDEP being developed by ICRP is noteworthy for the use of a new respiratory model and a user-friendly software.