We explored health care professionals' beliefs and methods for counseling patients about risks for transmitting human immunodeficiency virus (HIV) through oral sex and HIV-seropositive patients' beliefs and practices regarding oral sex behavior. Health care professionals used divergent counseling strategies, avoided specific recommendations, and expressed ambivalence about recommending barrier protection for oral sex. Patients expressed differing beliefs about oral sex risk; the majority have engaged in unprotected oral sex since diagnosis. Few professionals or patients mentioned oral sex risk for other sexually transmitted diseases (STDs), which can be cofactors for HIV. Although scientific evidence indicates a potential risk for transmitting HIV via oral sex, and patients in our sample want more information about this risk, the health care professionals we interviewed have adopted a largely noncommittal approach to communicating potential risk to patients. Health care professionals should consider discussing more specifically with patients the oral sex risk for transmission of HIV and other sexually transmitted diseases.