The prevalence of antibodies against herpes simplex virus type 2 (anti-HSV-2) among pregnant women in Norway is not known. To study the prevalence of anti-HSV-2, a random sample of 961 women was drawn from a study population of 35,940 pregnant women in Norway during 1992-94. 27% (256/961) had anti-HSV-2. The prevalence increased with age. 17% of the 20-24-year-olds and 34% of the 35 year-old or older had anti-HSV-2. The presence of antibodies also varied geographically, from 18% in the south to 39% in the north of Norway. Among women with repeated anti-HSV-2 tests during pregnancy, 2.6% of the seronegative women seroconverted (16/623). HSV-2 infection is common among pregnant women in Norway. The public health implications of this infection need to be clarified.