| Release date | Label | Catalog ID | Format | Description |
|---|---|---|---|---|
| July 14th, 1992 | Capitol Records | CDP 7 98531 2 | CD | |
| July 14th, 1992 | Capitol Records | C4-98531 | Cassette | |
| July 14th, 1992 | Capitol Records | CDP 598531 | CD | |
| July 14th, 1992 | Capitol Records | C2 98531 | CD | |
| July 14th, 1992 | Capitol Records | C3 0777 7 98531 3 7 | CD | Mini CD |
| July 14th, 1992 | Capitol Records | CDP 0777 798531 2 0 | CD | |
| July 14th, 1992 | Capitol Records | CDP 7 98531 2 | CD | Longbox |
| 1992 | Capitol Records | 7 98531 1 | 12" vinyl | |
| 1992 | Capitol Records | EKPL-0247 | 12" vinyl | |
| 1992 | Capitol Records | 798531 2 | CD | |
| 1992 | Capitol Records | 072 7985312 | CD | |
| 1992 | Capitol Records | 0777 7 98531-4 4 | Cassette | |
| 1992 | Capitol Records | C163340 | Cassette | |
| 1992 | Capitol Records | 066 79 8531 1 | 12" vinyl | |
| 1992 | Capitol Records | 0777 7 98531 1 3 | 12" vinyl | |
| 1992 | Capitol Records | 68 7985311 | 12" vinyl | |
| 1992 | Capitol Records | 070 798531 1 | 12" vinyl | |
| 1992 | Capitol Records | 33439 | 12" vinyl | |
|
1992
(titled "Countdown to Extinction (Cuenta Regresiva a la Extincion)") |
Capitol Records | 25913 | 12" vinyl | |
| 1992 | Capitol Records | 798531 4 | Cassette | |
| 1992 (Unofficial) | Elbo | 1093 | Cassette | |
| 1992 | EMI | 11001484 | 12" vinyl | |
| 1992 | EMI / Kemongsa Music Ltd. | EKPC-0247 | Cassette | South Korea |
| 1992 (Unofficial) | Euro Star | ES 1464 | Cassette | |
| 1992 (Unofficial) | Euro Star | ES 159 | Cassette | |
| 1992 (Unofficial) | LEO | 0813L92 | Cassette | |
| 1992 (Unofficial) | Mag Magic | MM-0961 | Cassette | |
| 1992 (Unofficial) | MG Records | MG 2240 | Cassette | |
| 1992 (Unofficial) | Nora Music | NM 210 | Cassette | |
| 1992 (Unofficial) | Orion | OR 0225 | Cassette | |
| 1992 (Unofficial) | Phonex | PH 0488 | Cassette | |
| 1992 (Unofficial) | ProCom | 627 | Cassette | |
| 1992 (Unofficial) | Star | 243 | Cassette | |
| 1992 (Unofficial) | Takt Music | 1845 | Cassette | |
| 1992 (Unofficial) | Tango Music | T-146 | Cassette | |
| July 8th, 1992 | Capitol Records | TOCP-7164 | CD | Japan |
| July 14th, 1992 | Capitol Records | C2-98531 | CD | Longbox |
|
1993
(Unofficial) (titled "Megadeth") |
Delta Music | MDM-100.005,- | Cassette | |
| 1993 (Unofficial) | Hiton | H 291 | Cassette | |
| 1993 (Unofficial) | Phoenix | 516 | Cassette | |
| 1993 (Unofficial) | Starling | S9061 | Cassette | |
| 1993 (Unofficial) | Vivo | 591 | Cassette | |
| 1995 (Unofficial) | Mad Vox | 513 | Cassette | |
| 1996 (Unofficial) | Angel's of Hell Records | 142 | Cassette | |
| 1996 (Unofficial) | Euro Sonic Production | Cassette | ||
| October 29th, 1997 | Capitol Records | TOCP-3344 | CD | Japan, Reissue |
| May 1998 (Unofficial) | Moon Records | Cassette | ||
|
2002
(Unofficial) (titled "Countdown to Extinction / No More Mr. Nice Guy & Anarchy in the U.K.") |
Agat Company | A-415 | CD | |
| 2003 (Unofficial) | Monsters of Rock Records | MOFR 0352 | CD | Special edition |
| 2004 | Capitol Records | 724359862026 | CD | Remixed, Remastered |
| 2004 | Gala Records | 0946334408 2 1 | CD | Remixed, Remastered |
| 2004 | Mobile Fidelity Sound Lab | UDCD 765 | CD | Remixed, Remastered |
| July 24th, 2004 | Capitol Records | 7243-5-79875-2-3 | CD | Remixed, Remastered |
| July 24th, 2004 | Capitol Records | 724359862026 | CD | Remixed, Remastered |
| August 25th, 2004 | Toshiba EMI | TOCP-67444 | CD | Reissue, Remastered, Japan |
| 2008 | Mobile Fidelity Sound Lab | MFSL 2-285 | 2 12" vinyls | |
| October 29th, 2008 | Toshiba EMI | TOCP-70630 | CD | Reissue, Remastered, Japan, Mini LP |
| December 8th, 2010 | Capitol Records | TOCP-54226 | CD | Japan, Reissue, Remastered |
| November 6th, 2012 | Capitol Records | 5099997848424 | 2CD | Boxed set, Twentieth anniversary edition, Cardboard sleeve, Remastered |
| November 7th, 2012 | Capitol Records | TOCP-71404 | 2CD | Japan, Boxed set, Twentieth anniversary edition, Remastered |
| June 12th, 2013 | Toshiba EMI | TOCP-95120 | CD | Reissue, Remastered, Japan, SHM-CD |
| November 10th, 2014 | Capitol Records | 0602537976478 | 12" vinyl | 180 gram picture disc |
| November 11th, 2014 | UMe | B0021517-01 | 12" vinyl | Limited edition, Picture disc, Reissue, US |
| February 22nd, 2023 | Capitol Records | UICY-80240 | CD | Japan, Limited edition, Reissue, Remixed, Remastered, Mini-LP, Slipcase, SHM-CD |
| March 10th, 2023 | Capitol Records | Digital | ATMOS & New Stereo Remaster | |
| April 7th, 2023 | Capitol Records | UICY-80240K | CD | Japan, Limited edition, Reissue, Remastered, Mini-LP, SHM-CD |
| Unknown (Unofficial) | Independent | CD | ||
| Unknown | Aquarius Musikindo | E1249 / TC-C4 98531 | Cassette | |
| Unknown | Capitol Records | Digital | Remixed, Remastered | |
|
Unknown
(titled "Countdown to Extinction (Deluxe Edition)") |
Capitol Records | Digital | Twentieth anniversary edition, Remastered | |
| Unknown (Unofficial) | Crystal Records | Cassette | ||
| Unknown (Unofficial) | GM Music | G-399 | Cassette | |
| Unknown (Unofficial) | King's Records | Cassette | ||
| Unknown (Unofficial) | Music World | MW 0375 | Cassette | |
| Unknown (Unofficial) | Rock Gallery | Cassette | ||
| Unknown (Unofficial) | Unison | 29 | Cassette | |
| Unknown (Unofficial) | Viva L.S.D. Records | Cassette | ||
| Unknown (Unofficial) | Vox Studio | Cassette |