In a study of patients with cervical intraepithelial neoplasia, Burger et al. (A-47) compared those who were human papillomavirus (HPV)-positive and those who were HPV-negative with respect to risk factors for HPV infection. Among their findings were 60 out of 91 nonsmokers with HPV infection and 44 HPV-positive patients out of 50 who smoked 21 or more cigarettes per day.