Various Cheats:
Enter the password: W93M 7H2O BCYO PSVB
This code gives you 100 health, 200 armor, all weapons, full ammo, the backpack, levels 29-31 finished, and takes you to the last level. Additionally, it gives you three pentagram items that make your laser three times as powerful as the BFG9000. The three pentagram items also enable you to use the three switches in the last level (and closes the gates that spawn the monsters).
Level Codes (Skill Level: "Be Gentle!"):
Level 2: cdp8 9bj2 68zt svk?
Level 3: cxm8 9bjy 681t jvk?
Level 4: ddk8 9bjt 683s 9vk?
Level 5: dxh8 9bjp 685s 1vk?
Level 6: fdf8 9bjk 687s svk?
Level 7: fxc8 9bjf 689s jvk?
Level 8: gd?8 9bc? 69br ?bk?
Level 9: gx88 9bc6 69dr 2bk?
Level 10: hd68 9bc2 69gr tbk?
Level 11: hx48 9bcy 69jr kbk?
Level 12: jd28 9bct 69lq ?bk?
Level 13: jx08 9bcp 69nq 2bk?
Level 14: kdy8 9bck 69qq tbk?
Level 15: kxw8 9bcf 69sq kbk?
Level 16: lft8 9bb? 69vp ?vk?
Level 17: lyr8 9bb6 69xp 2vk?
Level 18: mfp8 9bb2 69zp tvk?
Level 19: mym8 9bby 691p kvk?
Level 20: nfk8 9bbt 693n ?vk?
Level 21: nyh8 9bbp 695n 2vk?
Level 22: pff8 9bbk 697n tvk?
Level 23: pyc8 9bbf 699n kvk?
Level 24: qf?8 9bf? 6?bm ?bk?
Level 25: qy88 9bf6 6?dm 2bk?
Level 26: rf68 9bf2 6?gm tbk?
Level 27: ry48 9bfy 6?jm kbk?
Level 28: sf28 9bft 6?ll ?bk?
Level 29: sy08 9bfp 6?nl 2bk?
Level 30: tfy8 9bfk 6?ql tbk?
Level 31: tyw8 9bff 6?sl kbk?
Level 32: vbt8 9bd? 6?vk 9vk?
Level Codes (Skill Level: "Bring It On!"):
Level 2: cjpr 9bj1 68z? qvk?
Level 3: c1mr 9bjx 681? gvk?
Level 4: djkr 9bjs 6839 7vk?
Level 5: d1hr 9bjn 6859 zvk?
Level 6: fjfr 9bjj 6879 qvk?
Level 7: f1cr 9bjd 6899 gvk?
Level 8: gj?r 9bc9 69b8 8bk?
Level 9: g18r 9bc5 69d8 0bk?
Level 10: hj6r 9bc1 69g8 rbk?
Level 12: jj2r 9bcs 69l7 8bk?
Level 13: j10r 9bcn 69n7 0bk?
Level 14: kjyr 9bcj 69q7 rbk?
Level 15: k1wr 9bcd 69s7 hbk?
Level 16: lktr 9bb9 69v6 8vk?
Level 17: l2rr 9bb5 69x6 0vk?
Level 18: mkpr 9bb1 69z6 rvk?
Level 19: m2mr 9bbx 6916 hvk?
Level 20: nkkr 9bbs 6935 8vk?
Level 21: n2hr 9bbn 6955 0vk?
Level 22: pkfr 9bbj 6975 rvk?
Level 23: p2cr 9bbd 6995 hvk?
Level 24: qk?r 9bf9 6?b4 8bk?
Level 25: q28r 9bf5 6?d4 0bk?
Level 26: rk6r 9bf1 6?g4 rbk?
Level 27: r24r 9bfx 6?j4 hbk?
Level 28: sk2r 9bfs 6?l3 8bk?
Level 29: s20r 9bfn 6?n3 0bk?
Level 30: tkyr 9bfj 6?q3 rbk?
Level 31: t2wr 9bfd 6?s3 hbk?
Level 32: vgtr 9bd9 6?v2 7vk?
Level Codes (Skill Level: "I Own Doom!"):
Level 2: cnn8 9bj0 680t nvk?
Level 3: c5l8 9bjw 682t dvk?
Level 4: dnj8 9bjr 684s 5vk?
Level 5: d5g8 9bjm 686s xvk?
Level 6: fnd8 9bjh 688s nvk?
Level 7: f5b8 9bjc 68?s dvk?
Level 8: gn98 9bc8 69cr 6bk?
Level 9: g578 9bc4 69fr ybk?
Level 10: hn58 9bc0 69hr pbk?
Level 11: h538 9bcw 69kr fbk?
Level 12: jn18 9bcr 69mq 6bk?
Level 13: j5z8 9bcm 69pq ybk?
Level 14: knx8 9bch 69rq pbk?
Level 15: k5v8 9bcc 69tq fbk?
Level 16: lps8 9bb8 69wp 6vk?
Level 17: l6q8 9bb4 69yp yvk?
Level 18: mpn8 9bb0 690p pvk?
Level 19: m6l8 9bbw 692p fvk?
Level 20: npj8 9bbr 694n 6vk?
Level 21: n6g8 9bbm 696n yvk?
Level 22: ppd8 9bbh 698n pvk?
Level 23: p6b8 9bbc 69?n fvk?
Level 24: qp98 9bf8 6?cm 6bk?
Level 25: q678 9bf4 6?fm ybk?
Level 26: rp58 9bf0 6?hm pbk?
Level 27: r638 9bfw 6?km fbk?
Level 28: sp18 9bfr 6?ml 6bk?
Level 29: s6z8 9bfm 6?pl ybk?
Level 30: tpx8 9bfh 6?rl pbk?
Level 31: t6v8 9bfc 6?tl fbk?
Level 32: vls8 9bd8 6?wk 5vk?
Level Codes (Skill Level: "Watch Me Die!"):
Level 2: csnr 9bjz 680? lvk?
Level 3: c9lr 9bjv 682? bvk?
Level 4: dsjr 9bjq 6849 3vk?
Level 5: d9gr 9bjl 6869 vvk?
Level 6: fsdr 9bjg 6889 lvk?
Level 7: f9br 9bjb 68?9 bvk?
Level 8: gs9r 9bc7 69c8 4bk?
Level 9: g97r 9bc3 69f8 wbk?
Level 10: hs5r 9bcz 69h8 mbk?
Level 11: h93r 9bcv 69k8 cbk?
Level 12: js1r 9bcq 69m7 4bk?
Level 13: j9zr 9bcl 69p7 wbk?
Level 14: ksxr 9bcg 69r7 mbk?
Level 15: k9vr 9bcb 69t7 cbk?
Level 16: ltsr 9bb7 69w6 4vk?
Level 17: l?qr 9bb3 69y6 wvk?
Level 18: mtnr 9bbz 6906 mvk?
Level 19: m?lr 9bbv 6926 cvk?
Level 20: ntjr 9bbq 6945 4vk?
Level 21: n?gr 9bbl 6965 wvk?
Level 22: ptdr 9bbg 6985 mvk?
Level 23: p?br 9bbb 69?5 cvk?
Level 24: qt9r 9bf7 6?c4 4bk?
Level 25: q?7r 9bf3 6?f4 wbk?
Level 26: rt5r 9bfz 6?h4 mbk?
Level 27: r?3r 9bfv 6?k4 cbk?
Level 28: st1r 9bfq 6?m3 4bk?
Level 29: s?zr 9bfl 6?p3 wbk?
Level 30: ttxr 9bfg 6?r3 mbk?
Level 31: t?vr 9bfb 6?t3 cbk?
Level 32: vqsr 9bd7 6?w2 3vk?
Various Cheats:
Enter the password: ?TJL BDFW BFGV JVVB
This code enables all the big ones: God Mode, all levels, all weapons, all ammo, full maps, and full health.
Level Codes:
Here are the level codes (levels 1-8) for the hardest setting on Doom 64.
The Terraformer: CB92 NBPL SYL? JO27
Main Engineering: BXYH ?G41 6Z4J PJ?Z
Holding Area: CYCC MGPK X47G TS2B
Tech Center: CF3? PG6D S12Z PFKB
Alpha Quadrant: BXRO TH1F 52GG 7W?B
Research Lab: BBXW HLGS XB8F 4RKB
Final Outpost: FVV9 FL55 QGFV DWJB
Even Simpler: FFLB MQ6C VV1C PF1B