Maxim Magazine relied on The Clothing Doctor, Steve Boorstein, in a discussion on dry cleaning in it's "Ask Us Anything" column:

"The term dry cleaning is kind of a misnomer," admits Steve Boorstein, a fourth-generation dry cleaner and the author of The Ultimate Guide to Shopping and Caring for Clothing. "It refers to the nature of the cleaning solvent, which is highly evaporative and not water-soluble." Dry cleaning machines look like front-load washing machines but use solvents containing percholoroethylene or tetrachloroethylene--or a somewhat less toxic petroleum-based concoction. Since the solutions aren't absorbed by fabric and evaporate easily, they prevent shrinking and stretching.

After being washed, clothes are steamed and pressed for that woefully unhip "clean" look. Since dry cleaning is safe for most fabrics, some manufacturers slap dry-clean-only tags on all their clothing. But if it isn't wool or silk, it may not need to be dry cleaned--so wash that tuxedo T-shirt to your heart's content.