GHRI stained silk blouses, white cotton shirts, and wool skirts (with ink, coffee, lipstick, cooking oil, and wine) and took them to five types of cleaners, with instructions not to pretreat. Here are our findings:

Perc: The Traditional Method

About 85 percent of all dry cleaners use perchloroethylene (perc), a powerful cleaning agent. When it's used properly, very little of the chemical is left on clothing, and it hasn't been shown to be harmful to wearers. However, its use is strictly regulated because if not handled carefully, perc can be a toxic environmental pollutant and dangerous to workers, with chronic high exposure causing serious health effects (headaches, nausea, lung and eye irritation, liver and kidney damage) and, likely, cancer. Because of the risks, a federal law mandates the phasing out of perc-based cleaners located in residential buildings by 2020. If you have your clothes cleaned with perc, it can't hurt to remove plastic to air them before wearing or storing. "It's also better for the fabric, as plastic can hold in moisture and cause mildew," says Kathleen Huddy, GHRI Textiles Director.

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How it cleaned on our tests: A known degreaser, perc fared best on oil and lipstick stains. Coffee also released readily, but ink and wine yielded less easily, particularly on silk and cotton.

How Green Are the Alternative Dry-Cleaning Processes?

"The class of chemicals that act as strong solvents can be harmful to people and the environment," says Clive Davies, Chief of the Design for the Environment Program at the Environmental Protection Agency (EPA). "The challenge is to come up with a process that gets clothes clean with little or no negative impact." These are the alternatives currently available:

More From Good Housekeeping

1. Wet Cleaning: a water- and detergent-based process that's considered a safer alternative by the EPA.

How it cleaned on our tests: Wet cleaners removed coffee and wine pretty well from all. Oil, lipstick, and ink (the toughest stain to remove) were less likely to come out. Note: While we didn't experience any problems in our test, wet cleaning may shrink, fade, warp, or discolor some fabrics, such as rayon, acetate, and some silks. A skilled cleaner can tell you if it's a risk.

2. Liquid CO2, a process also considered safer by the EPA, reuses most of its CO2, so very little is released into the atmosphere.

How it cleaned on our tests: Liquid CO2 cleaning erased lipstick, oil, and coffee from all three fabrics, but tended to leave some ink and wine behind. While all methods caused minimal shrinkage, CO2 had the least.

3. Liquid Silicone: a proprietary cleanser under the brand name GreenEarth, claims to degrade to sand, CO2, and water, making it a low pollution risk. Its health effects, however, aren't yet fully researched, which is why the EPA hasn't taken a position on it.

How it cleaned on our tests: GreenEarth's process proved to be the cleaning champ, conquering coffee, lipstick, and oil with ease. It also removed most of our wine stains, but wasn't great at zapping ink from silk.

4. Perc-Alternative hydrocarbon solvents are an easy swap for cleaners, as they can continue to use existing perc machines. These chemicals, such as propylene glycol, are petroleum-based like perc and must be handled with care, but are engineered to biodegrade much more quickly than perc.

How it cleaned on our tests: Perc-alternative hydrocarbon dissolved oil and, in general, worked best on stains in wool. However, cotton and silk remained soiled, with ink and wine barely budging.

The Bottom Line

Claims of "green" and "organic" dry cleaning are currently unregulated, and often used improperly. "The word 'organic' sounds like an apple that's grown without pesticides," Davies says. "Chemically, it just means something is made with hydrocarbons, not that it's necessarily somehow safer." Ask the dry-cleaning store you frequent what method they use (they may not advertise this fact clearly)—and if they can't or won't tell you, think twice. By our analysis, Liquid CO2 provides the best combo of environmental safety and good cleaning results. An experienced wet cleaner is also a worthwhile (and possibly easier-to-find) option.

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