Canon Digital Slr Flash
A TTL flash work with digital SLR (Canon)?

I have Canon 35mm SLR (EOS Elan II) and I use PowerZoom Sunpak 4000AF flash with it. I have the intention Upgrading to DSLR (probably Rebel XTi). Would you be able to use the same flash Sunpak with DSLR?

Since both cameras have E-TTL flash metering the Sunpak should work. However, to be sure, it is necessary to check the trigger voltage of the flash and see what is on the XTi. If the trigger voltage is too high can damage your new camera. IMO should consider selling the Sunpak and buy the flash that offers for Canon XTi.