BACKGROUND: Women accessing the public health system in Gauteng province, South Africa are largely unscreened for cervical cancer and have a high background prevalence of human immunodeficiency virus (HIV) infection. OBJECTIVES: This cross-sectional study describes the age-specific prevalence of human papillomavirus (HPV) infection and cytological abnormalities among this urban and peri-urban population. METHOD: Over the period March 2009 - September 2011, 1 524 women attending public sector primary healthcare clinics were invited to participate in a cervical cancer screening study. All participants were screened with conventional cytology and HPV testing undertaken using the HPV linear array genotyping kit (Roche Molecular Systems). RESULTS: Of 1 472 women with valid cytology results, abnormalities were detected in 17.3% (n=255), of which 9.1% (n=134) were high-grade squamous intraepithelial lesions, and 0.5% (n=8) suggestive of squamous carcinoma. Of the 1 445 women with complete data, the overall and high-risk HPV DNA prevalences were 74.6% (n=1 078) and 54.3% (n=784), respectively. HPV type 16 and/or 18 were detected in 19.5% (n=282) of women. Age-specific prevalence of HPV showed a plateau-shaped curve. CONCLUSIONS: The prevalences of HPV infection and abnormal cytology were much higher than previously reported in general populations in South Africa and elsewhere. Higher age-specific prevalence and similar plateau-like age-specific epidemiological curves have previously only been described in studies among HIV-positive women. These findings have implications for planning and development of cervical screening programmes in developing countries with largely unscreened populations with a high background prevalence of HIV.