The Tritium Migration Analysis Program (TMAP) was an aid in performing safety analyses of fusion systems using combined heat and mass transport calculations. Upgraded to TMAP4, it was verified and validated at the INEEL. The further upgrade of the code to TMAP2000 was accomplished in response to several needs. TMAP and TMAP4 had the capacity to deal with only a single trap for diffusing gaseous species in solid structures. TMAP2000 has been revised to include up to three separate traps and to keep track separately of each of up to 10 diffusing species in each of the traps. The original code experienced problems in dealing with heteronuclear molecule formation such as HD and DT. That has been corrected. A further sophistication is the addition of non-diffusing surface species and surface binding energy dynamics options. TMAP2000 will accommodate up to 30 such surface species. Additionally, TMAP2000 allows simulation of surface fluxes dependent on a surface binding energy and an adsorption barrier energy. All of the previously existing features for heat transfer, flows between enclosures, and chemical reactions within the enclosures have been retained, but the allowed problem size and complexity have been significantly increased to take advantage of the greater memory and speed available on modern computers.