A Counter - Petition for Dissolution of Marriage is sometimes used in Illinois divorce cases. It means that you filed for divorce from your spouse first, making you the Petitioner, and now your spouse wants to have their own Petition for divorce on file. The counter - petition will have the same case number and is not treated like a separate proceeding. I usually use it in my divorce practice as "insurance" against the first Petitioner dismissing their case. So, if wife sues for divorce and things have been moving along in the process for a while and then the wife decides that she is going to withdraw her divorce petition, then all of the progress that has been made to that point, legally, is gone. If the husband had filed a Counter - Petition, then even if the wife withdrew her Petition, the husband can still move forward presuming that he still wants to be a divorce. It is also used as a way for people to put in their own grounds for divorce.