It's a question worth posting: Just how dirty can a shower curtain get? After all, it's in the shower -- a place specifically designed for a good scrubbing.
Turns out, shower curtains are magnets for mildew and grime. If you're in doubt, inspect the folds and seams of your shower curtain and see what you find. Eww!
The good news is that shower curtains are one of the easiest things to clean. If your shower curtain is made of a natural fabric like hemp or cotton, launder it in hot water in a washing machine. If the mildew has begun to colonize and form a political system, add a quarter-cup of bleach to the water. If it is only loosely organized, ordinary laundry detergent should work fine.
Surprisingly, you also can launder vinyl or synthetic shower curtains, as long as you keep the water warm. Pay attention to vinyl shower curtain liners, too, by scrubbing them with a 1:10 bleach-to-water ratio [source: Martha Stewart].