AIDS: At a recent HIV workshop held in Chicago, IL, researcher David G. Ostrow discussed the results of four clinical studies on oral sex that yielded a range of conclusions. Of the 548,102 AIDS cases that have been recorded in the United States, between 3 and 17 cases occurred because of oral sex. Workshop speakers noted that there is a much smaller amount of pre-ejaculation fluid than previously thought, and that not all men pre-ejaculate. The workshop offered some basic oral sex guidelines, including waiting two hours after brushing or flossing the teeth, spitting out, and cleansing the mouth with hydrogen peroxide.