Ninja Gaiden II: The Dark Sword of Chaos Cheats

Lighting occasionally illuminates the dark screen in Stage 3-1. Pause the game and wait for the lightning to come.

Near the end of stage 4-2, there's a 1UP. Get it, and then go back up the ladder and out of that area. Return, and the 1UP will be there again. Repeat this process until you have as many lives as you need.