Tritium in the form of metal tritide particles presents a peculiar problem for the calculation of internal dose. Standard calculations indicate that just a few 3 to 5 micron sized particles appears to lead to a very large dose. There are very few data on which calculations can be based. It will be shown that the biological effectiveness for β radiation that actually escapes from the metal particles is greatly reduced. Rather than having the standard value of one, the effective value is of the order of 10−4. Additional calculations show the bremsstrahlung radiation forms a part of the dose from tritided particles about equal to the mitigated part from ion production.