Detailed information on the menstrual bleeding patterns in users of copper-releasing intrauterine devices (IUDs) and levonorgestrel-releasing intrauterine systems (IUSs) is lacking. Even less is known about the menstrual bleeding patterns associated with postabortal insertion of IUDs. We postulated that the scarcity of IUD studies including detailed analysis of bleeding could be a result of the lack of an easy-to-use computer program designed for this purpose. We therefore developed a set of graphical user interface (Windows) programs for entering, editing, and analyzing menstrual diary data. With these programs, we reanalyzed the menstrual diaries of the subjects of one of the hospital clinics that participated in a previous multicenter study comparing copper IUDs and LNg IUSs. The group included patients who had the IUD inserted postabortally. Copper IUD users had patterns of bleeding that were stable over time, and clearly more bleeding than LNg IUS users, many of whom had either infrequent bleeding, bleeding completely replaced by regularly occurring spotting, or amenorrhea. Postabortal insertion of LNg IUSs was associated with slightly better patterns of bleeding than postmenstrual insertion. Detailed statistics on bleeding help clinicians in counseling patients regarding these methods. The statistics permit assumptions to be made about the probabilities of specific menstrual disturbances and their changes over time.