['We previously reported that higher circulating concentrations of folate are independently associated with a lower likelihood of becoming positive for high-risk human papillomaviruses (HR-HPVs) and of having a persistent HR-HPV infection and a greater likelihood of becoming HR-HPV negative (Cancer Res 2004;64:8788-93). In the present study conducted in the same study population, we tested whether circulating folate concentrations modify the risk of cervical intraepithelial neoplasia (CIN) > or =2 associated with specific types of HR-HPV.', 'Multiple logistic regression models were used to assess associations (odds ratio with 95% confidence intervals) across HR-HPV, folate, and rigorously reviewed cervical histology of each subject.', 'HPV-16-positive women with low red blood cell folate were significantly more likely to be diagnosed with CIN > or =2 than were HPV-16-negative women with higher red blood cell folate (odds ratio 9, 95% confidence interval 3.3-24.8).'] Does lower red blood cell folate enhance the HPV-16-associated risk of cervical intraepithelial neoplasia?