Information about vulvovaginal and perianal condylomata acuminata and intraepithelial neoplasia in women infected with HIV-1 is needed to develop guidelines for clinical care. Our aim was to investigate the incidence of these lesions in HIV-1-positive and HIV-1-negative women and to examine risk factors for disease. In a prospective cohort study, 925 women had a gynaecological examination twice yearly-including colposcopy and tests for human papillomavirus DNA in cervicovaginal lavage-for a median follow-up of 3.2 years (IQR 0.98-4.87). Vulvovaginal and perianal condylomata acuminata or intraepithelial neoplasia were present in 30 (6%) of 481 HIV-1-positive and four (1%) of 437 HIV-1-negative women (p<0.0001) at enrollment. Women without lesions at enrollment were included in an incidence analysis. 33 (9%) of 385 HIV-1-positive and two (1%) of 341 HIV-1-negative women developed vulvovaginal or perianal lesions, resulting in an incidence of 2.6 and 0.16 cases per 100 person-years, respectively (relative risk 16, 95% CI 12.9-20.5; p < 0.0001). Risk factors for incident lesions included HIV-1 infection (p = 0.013), human papillomavirus infection (p=0.0013), lower CD4 T lymphocyte count (p = 0.0395), and history of frequent injection of drugs (p=0.0199). Our results suggest that HIV-1-positive women are at increased risk of development of invasive vulvar carcinoma. Thus, we recommend that, as part of every gynaecological examination, HIV-1-positive women should have a thorough inspection of the vulva and perianal region, and women with abnormalities-except for typical, exophytic condylomata acuminata-should undergo colposcopy and biopsy.