How do you delete all pokedex data in the game?

I don't think you can delete it.

As soon as you turn the Gameboy on hold up, left, select, and start at the same time. You will be asked if you want to erase all data. Say "yes."

Right after the "Game Boy" title screen disappears, hold up, right, A, and B at the same time. It will ask you if you want to erase all data. Press A for yes, B for no.

Haha nice try. You can't hold up ad left at the same time. I don't know how to erase pokedex I'm still looking 4 that but to erase high scores hold b at the start screen. You will go to the high scores list.THEN LET GO OF B.then hold start and select AT THE SAME TIME and it will say erase data? Yes no? Choose yess and the hiscore list will go to defalt. (gam is a defalt person as well as the others) hope you find the pokedex erase code! (I bought a used game as well, and if you find it plz tell me because my pokedex is halfway done as well and thats bad :( )

Before the copyright screen, after the game boy logo, hold up, right, Start and Select at the same time. That'll bring up the "erase all data?" option. That means Pokedex AND scores. Just did it on the used copy I bought.

It doesn't work. Pressing start and select at the sametime.

The logo under Gameboy (Nintendo°) dissapears but it doesn't ask me to erase data.

Up/Right/Start/Select is the one that worked, thanks.

No bs up right start select just as you turn on the game boy works. Just mash that dpad and start and select and it says erase all data? Yes A No B. Thank you!

I tried a few that turned out to be bogus - up, right, select and start as soon as the 'game boy' logo disappears (before the copyright info) - youll get a black screen and "erase all data? B yes, a no"

I got frustrated with this, but Up, Right, Start, and Select work. You just have to be super quick. Right when you can no longer see the GAME BOY on the title screen, hold the above buttons. If the screen turns black before you press said buttons, then it may not work. If you see the copyright screen, then you are too late.

I just tried the up,right,select,start trick right now and it totally worked. Right after the game boy logo dissappears and before the copyright screen appears.

You have to go on pokedex then hold left and press l and r at the same time repeatedly and it will ask if you want to delete data and say yes

Confirmed that going to either the pokedex or hi score screens and pressing left L and R all at the same time repeatedly will prompt for respective deletion. The start select option doesn't appear to work on gameboy DS. (perhaps not properly emulated...)

To clear it up since I'm seeing a lot of different answers:

For the ORIGINAL Pokemon Pinball for Game Boy, hold Up+Right+Start+Select as the Game Boy logo disappears, before the copyright screen.

For the GBA Pokemon Pinball Ruby/Sapphire, go to the Pokedex or Highscore screen and hold Left+L+R.