Are PAL region Mega Drive games region locked or otherwise incompatible with my Genesis?

[The Adventurer]

I sort of want to track down a few PAL region Mega Drive games (See: Wily Wars, also Pulseman) and was just wondering if they are natively compatible with my US Genesis.

[Scissors]

Some will work fine, others won't. I believe Wily Wars is one of the ones that won't work, but you could probably get it to work with a Game Genie and a code to bypass the lockout. As for Pulseman, I don't think that ever got a PAL release. The Japanese version can be played with a Game Genie though.

[theclaw]

Typically PAL games were not reprogrammed. 50hz causes most to play slower than their creators intended.

Regions have other effects too.
Genesis inherited the idea from Master System. So it supports dual-language SMS games.
In addition Sega CD drives use region lock. Their BIOS won't load if they detect a wrong console.