A pre-existing condition is a health condition or illness that a person has had before a certain point. That point may be at the time they apply for health insurance coverage. It may be at the time they are involved in an auto accident. It may be prior to the point of applying for life insurance. With regard to health insurance coverage, a pre-existing condition can be quite costly. This is why some people, who have a pre-existing health condition or illness, are denied coverage. Some insurance providers will agree to provide coverage, but will limit or exclude their responsibility to be liable with regard the pre-existing condition. The healthcare industry is complex, thus making it hard to determine which category your pre-existing condition or illness would place you in.