Slave Flash Question with 580EX II and 430EX

I've had a 430EX Canon for about a year now, and recently I've decided to upgrade to the 580EX II. How can I use the 430EX as a flash slave with the new 580EX II? Do I need to buy an additional device or are there settings I need to change on the flash units?

If I can not use the 430EX as a slave then I am going to sell it.

Any replies would be appreciated. TIA

There's a switch on your 430; set to SLAVE.

Fire away with the 580.

Check the manuals for all the details on how-to, but it works.

You need to set the 430 to slave, and the 580 to master.

On the old 580 and 550 this was easily done with a switch near the hot shoe.
The 580EX II is a little different.
You need to hold down one of the buttons for 5 seconds for it to enter master mode.
(I have no idea which one, but I figured it out on a friends flash in the same time it took him to look it up in the manual).

Remember you also get to control ratios, groups etc, it pays to have a good read up first.