Last month, Sunday Source offered tips for finding a great roommate. But what happens when a good roommate turns bad (or a bad one, even worse)? To find out how awful communal living could get, we solicited your horror stories. And boy, did you deliver: We heard about one "cheap, horny and slothlike" guy in Baltimore who hit on his female co-habitants and was perpetually broke. A reader in Potomac remembered sharing a dorm room with a fragrant freshman who would dip into her dirty laundry basket for "fresh" underwear. But the jackpot in the bad-roommate lottery goes to the American University grad whose college dormmate started dressing like her -- right down to the same eyeglasses. Things really got creepy when Ms. Look-Alike began bringing home our reader's ex-boyfriends and inviting her to join in three-way make-out sessions. Nice.

So, how do you go about exorcizing a hellish roommate from your home or apartment? It can be tricky, especially if you're locked into a long-term lease with said ogre. But the situation isn't completely hopeless. Before you go changing the locks in the middle of the night (which you actually should never do, for legal reasons), here are some tips for ensuring that a bad housemate exits as peacefully as possible -- and without kicking your pooch on the way out.

COMMUNICATE CONSTRUCTIVELY. Resolving issues requires roommates to speak (or at least write) their piece. Expressing anger passive-aggressively via "misplaced" dirty Q-tips or unwashed dishes is rarely productive. Instead, Shauna Carmichael, a community mediator with the Northern Virginia Mediation Service, recommends honesty, as well as using "I feel" statements rather than the more-accusatory "You" statements. "I feel that our living situation isn't working out; I would like you to find a new place to live," will probably go over better than "You're a jerk who eats my food and uses my towels; you need to move out of my apartment in a month." (Note: Saying "I feel that you are a jerk" is not acceptable.)

TALK TO YOUR LANDLORD. Your landlord probably won't want to hear about your problems divvying up the cable bill, but he or she may be able to evict a roommate who is violating specific terms of the lease, such as willfully damaging the property or engaging in illegal activities. "If your problem [with the roommate] is a problem for the landlord as well, then you can enlist the landlord's help in filing for an eviction," says Janet Portman, a lawyer and co-author of "Every Tenant's Legal Guide" (Nolo.com, $29.99). But be warned that under a typical lease "all tenants [are] responsible for the sins of everybody else," says Portman. That means if there's a violation of the lease, the landlord has the right to evict all tenants, not just the responsible party.

SUBLET AT YOUR OWN RISK. Lots of people sublet their apartments or homes to roommates, but the practice can create headaches if either party wants the other to move out. If you're stuck in this situation, the best advice is to tread carefully as the legal issues can become complex. Under most leases, renters may not sublet space to extra roommates without notifying the property owner. Doing otherwise is a violation of the lease, for which the original renter can be evicted. In addition, the original renter is legally responsible for damages done to a property: If your misbehaving sublessee happens to leave any wine stains behind, you'll be the one the landlord sticks with the cleaning bill. Before taking any action, you may want to contact a lawyer or a tenant's rights organization such as the D.C. Tenants Advocacy Coalition to examine your options.

MEDIATE A RESOLUTION. If you and your roommate are stuck in a long-term lease and are unable to resolve your differences, consider mediation. Both parties sit down with a trained moderator who facilitates the airing of dirty laundry and helps craft a solution that everyone can agree upon. Carmichael says that mediation can be used preventatively to resolve household issues such as who takes care of the yard or how the bills are divided, or as an end-of the-road measure to negotiate the terms of a move-out. Either way, because there's no solution unless both parties come to an agreement, most people walk away from the process satisfied. "Sixty to 70 percent of people who use mediation are able to reach an agreement and are more content than if they went into a court," Carmichael says.

Bridget Bentz Sizer

KEY IN ON THE ISSUES

ApartmentReviews.net. Offers specific examples of subletting agreements and what they mean for all of the parties involved. www.apartmentreviews.net/roommates-rent-payments.htm.

D.C. Tenants Advocacy Coalition. A nonprofit organization dedicated to tenant-rights issues in the District. 202-628-3688. www.tenac.org.

Georgetown University. The Division of Student Affairs has helpful tips on being a good roommate and talking through a conflict. Best advice: Be calm and cool. www12.georgetown.edu/student-affairs/reslife/roommates.html.

Maryland State Bar Association. A straightforward list of the rights of tenants and landlords is on its Web site. www.msba.org/departments/commpubl/publications/brochures/landlordtenants.htm.

Northern Virginia Mediation Service. Free community mediation is available for roommate issues with less than $2,000 at stake. NVMS accepts cases from Northern Virginia, as well as the District and Maryland. 703-993-4394. www.nvms.us.

Virginia Department of Agriculture and Consumer Services. The Office of Consumer Affairs Web site has a list of frequently asked questions (and answers) for landlords and tenants. www.vdacs.virginia.gov/consumers/f-landlord.html.

Hastily packing up that annoying roomie's stuff so you can chuck it on the sidewalk is probably not the best way to go.