Hi Helen from Chicago: I think it depends on the group policy. I'm not sure how it is now with mine because I've been with the same group for over 20 years and it has changed many times. However, in the past the pre-existing condition clause covered a period of 3 months. (or possibly 6, I can't remember for sure) If you joined the group with a pre-existing condition it would not cover it for either 3 or 6 months. Once you reached a certain amount of out of pocket expenses (something like $3,000) it covered you regardless of the amount of time you were in the group. As I said it may not be the same now. I guess you really have to inquire.