Red Dragons are found in the Lunar Subterrane in the final stages of the game. They can show up by themselves, or in groups of two to three. In the original SNES version, the J2e translation, and the PlayStation translation, the Red Dragon sprites were too big to place two or three on the screen, so they overlapped, creating the illusion of only one Red Dragon being present (this also occurs in the PSP version if there are three Red Dragons in a battle). Like all enemies found in the core of the Lunar Subterrane, fights with Red Dragons have boss music, rather than the normal battle music.
Red Dragons can be a very difficult enemy to face, unless the right strategy is implemented. The first measure would be to cast Berserk on them. This will prevent them from using their Thermal Ray attack. Their weakness to Ice may then be exploited with Rydia's Blizzaga and Edge's Flood. It is also possible to Paralyze them, with the Mindflayer summon being the preferred method.
In the Nintendo DS version, an easier method consists of Cecil having the Draw AttacksAugment and then using defense the whole fight until Rosa can cast Berserk on it. This renders the dragon unable to use Thermal Ray. Alternatively, Rydia can summon Mindflayer to paralyze Red Dragon as well for a short time, giving the party time to prepare and giving Rosa time to use Berserk and Slow on it.