Risk factors for genital human papillomavirus (HPV) types 6/11 and 16/18 and any HPV type as well as for herpes simplex virus type 2 (HSV-2) infections were investigated in a population-based study of 1,600 randomly selected women (20-39 years) from Godthåb (native, Nuuk), Greenland, and Nykøbing Falster, Denmark. A total of 586 Greenlandic women and 661 Danish women were included, respectively. They all had a personal interview and a gynecologic examination with cervical smear and swab for HPV analysis (filter in situ hybridization). Moreover, a blood sample was obtained for analysis for HSV-2 antibodies by enzyme-linked immunosorbent assay. In view of the general concept of HPV as a sexually transmitted virus, it is unexpected that women with "multiple" partners revealed a significantly lower risk for all types of HPV than did women with "few" partners, the odds ratio (OR) being 40-60% decreased in women with greater than or equal to 30 partners compared with women who had 0-4 sexual partners. In contrast, the risk for HSV-2 infection was significantly increased among women with early age at first sexual intercourse (OR = 2.9 for age less than or equal to 13 vs. 14-16 years) and multiple partners (OR = 2.6 for greater than or equal to 20 vs. 0-4 partners) (hereafter referred to as "high sexual activity" as well as with an increasing number of sexually active years with an unprotected cervix (i.e., without the use of barrier contraceptives) (OR = 2.0 for greater than or equal to 15 vs. 0-9 years). The results of this study thus demonstrate a surprising risk pattern for HPV types 6/11 and 16/18, but a pattern for HSV-2 in line with that to be expected for a sexually transmitted virus. This could indicate the existence of factors, especially in women with high sexual activity, which interfere with the expression of HPV or with the ability to detect it and/or that HPV may be transmitted by means other than sexual contact.