There are two types: PCI cards (you buy one and can connect a second monitor->some PT users experiment "PCI too busy..." messages when using those) and AGP cards (that will replace the one delivered with your G4->two monitors can be connected on that same card->the good thing is that they don't take a PCI slot and don't use the PCI bus->the bad news is that they are more expensive than the PCI ones). Your call... I personnally own the AGP card from Promax (DHMAX for G4) and after a year of weird behaviour (the Finder would quite on a regular basis->nothing fatal, just annoying), it's now running without problem on my G4...couldn't work without it now.
If you go the PCI route I can recommend the Radeon 7000 mac by ATI. I've had mine for about 8 months now and it works great... you can even attach a TV to the card, so if you wanted, you could have your original screen, a second one AND a TV! //NW
Which computer? Additional PCI monitor cards are not supported with AGP G4's. As Mr T mentioned, you'll run into the dreaded "DAE -6042 PCI bus too busy" error. For information on supported dual channel AGP cards, go here: Scroll down to "Dual Monitor AGP Graphics Cards." -Jordan
------------------------------ Randy V. San Diego, CA '98 740iL (Black/Tan/NAV-TV & all the gadgets)