The following are known Game Genie Codes for Back to the Future II & III on Nintendo Entertainment System (NES).

• 20 Lives
  ZAXKZZPA
• 30 Lives
  LAXKZZPA
• Infinite Lives
  SXXELOVK
• 20 Nuclear Fuel Units
  ZAXKYZPA
• 30 Nuclear Fuel Units
  LAXKYZPA
• Quicker Shots
  PEKASEPO
• Keep Shots
  GZKAKGSA
• Infinite Fuel
  GZEEPZST
  GZOEZZST
• Start With 7? (The 2nd Item Over From Your Lives)
  YAXKGZPA
• Start With Most And A Lot of Items
  IAXGAZAA
• Starting Location Modifier
  AOSKLOYA
  Note: You can change the 1st, 2nd, and 8th letter of the code to start at different places.
• Start With 9 Trophies, And 9 of Each Item To The Right of The Trophies
  PEUKIPAE
• Infinite Keys On Pickup
  SXEEAXSE
  Note: This only works for the keys in the ones column of the key meter.
• Infinite Time In Puzzle Rooms
  SZUUUVVK