I bought two identical 5850s - one came with cables, one didn't.
![Huh](https://bitcointalk.org/Smileys/default/huh.gif)
Most newer PSUs have either adapters or existing molex for video cards. Depending on the PSU, they generally have at least one if not two. If your PSU says "CrossFire/SLI" on the box, you definitely should have at least 2.
That being said, go check your PSU to see how many 6 pin power cables you have and find somewhere to buy these guys in case you find yourself shorted.
![Smiley](https://bitcointalk.org/Smileys/default/smiley.gif)