According to http://www.fwhc.org/birth-control/iudinfo.htm (A very informative site regarding IUDs from the Feminist Women's Health Center) IUDs are 99.2-99.9% effective as birth control. They do not protect against sexually transmitted infections, including HIV/AIDS. Personally have had one for almost three years and no babies! See http://www.fwhc.org/birth-control for a chart of many birth control options.