You must make an honest assessment -- screamishness and squeamishness aside -- of the seriousness of the critter problem.

If your apartment is unfit or uninhabitable, you may use a legal procedure called "repair and deduct." In most states that have this law, and in NYC, it works like this: If the landlord has failed to fix a truly significant problem, you may, without permission and without filing a lawsuit, have defects or other problems repaired and subtract the cost of the repairs from the next month's rent.

But to be justified in using the repair-and-deduct remedy, the problem must be serious, not just annoying, and it must threaten your health or safety. The occasional cockroach -- even the occasional not-so-little cockroach -- doesn't justify using repair and deduct. But an ongoing infestation of insects or rodents is serious, since it presents a potential health hazard.

Before hiring an exterminator, you must give the landlord notice of the problem and provide access to your apartment. Put your complaint in writing and tell the landlord that if the problem is not addressed within a reasonable period of time -- ten days or so -- you will arrange to have the work performed and will deduct the cost from your next month's rent. Make sure to get dated receipts from contractors for any work performed so you can substantiate your rent deduction.

Alternatively, you may file a complaint with the NYC Department of Housing Preservation and Development (HPD). That will trigger an inspection of your unit. If the inspector finds that your apartment is infested, HPD will issue a violation ordering the landlord to correct the condition within a specific time -- usually 30 days or so, depending on the problem. If the landlord does not correct the problem within the time provided, HPD fines the landlord.