I can't seem to capture Regirock. I get him down low, and chuck at least..

Try paralysing or putting him to sleep. Since it has the Ability Clear Body, you can't lower its stats, but they will go down with Curse and Superpower.

Well first off, how did you get thirty Masterballs. Second, if you did throw a masterball, you would have caught it no problem. Third of all, just because it has low health, doesn't mean you catch it. Try putting it to sleep or use timerballs.

First of all you THROW the master ball. Second of all if you really have the game you would know that a master ball catches without fail. And finally you can only get 1 master ball. Do you have AR.........let me answer..no.

If you are using master balls he is yours.

First of all, if you were using master balls, only one would do the trick no matter what-even from full health. Without using a master ball, you can still capture it by weakening it to orange or red hp levels and using ultra balls. If you want to, switch to timer balls after 30-40 battle sequences have passed, and if you run out of these, just throw any balls you have on hand.

I think you must be mistaken in thinking in that u are using Master Balls, coz they always work. But I reccomend using Timer Balls. They're great. They don't work at first but they get better.

First of all, you certainly haven't been throwing master balls, they would've caught him on the first try. Second, If you threw 30 ultra balls or something, throw a timer ball. your taking so many turns that the timer ball will catch it easily.

Masterball have a 100% chance of catching any pokemon.

Use timer balls and ultra balls.. Although I caught him with a pokeball. So have lots of those too...and it takes like half an hour to catch them anyway.

What I advise is that you bring a pokemon at least 10 levels higher than Regirock that has attacks such as sleep powder/hypnosis, and another pokemon (around the same level as Regirock) who's element is water, ice or grass. Get Regirock's health down as low as you can (like you said you did) and put him to sleep.

Then sit back and throw a variety of balls. Use timer ball if the battle goes on for AGES, but ultra ball should do.

NOTE: The ball throwing part really depends on luck though. I caught Kyogre with an ultra ball, and on Pokemon Silver I caught Lugia with a Great ball. On pokemon yellow I caught Articuno (which was burnt) with a Poke Ball!
Good Luck in catching Regirock!

OK first things first save before you fight him and go catch an electrike. Put electrike first in your party and let regirock kill it. If your lucky regirock might get paralyzed due to electrikes ability Another way to do it is to get a heart scale (these can be found almost anywhere underwater) and go catch a altaria at sky pillar. go to fallobar town and go to the move tutors house and teach your altaria sing. Go back to regirock and put it to sleep and buy at least 25 ultra balls.