Understanding the fraction of newly detected human papillomavirus (HPV) infections due to acquisition and reactivation has important implications on screening strategies and prevention of HPV-associated neoplasia. Information on sexual activity and cervical samples for HPV DNA detection using Roche Linear Array were collected semiannually for two years from 700 women ages 35 to 60 years. Incidence and potential fraction of HPV associated with new and lifetime sexual partnerships were estimated using Poisson regression. Cox frailty models were used to estimate hazard ratios (HR) for potential risk factors of incident HPV detection. Recent and lifetime numbers of sexual partners were both strongly associated with incident HPV detection. However, only 13% of incident detections were attributed to new sexual partners, whereas 72% were attributed to 5 or more lifetime sexual partners. Furthermore, 155 of 183 (85%) incident HPV detections occurred during periods of sexual abstinence or monogamy, and were strongly associated with cumulative lifetime sexual exposure [HR: 4.1, 95% confidence interval (CI): 2.0-8.4). This association increased with increasing age. These data challenge the paradigm that incident HPV detection is driven by current sexual behavior and new viral acquisition in older women. Our observation that most incident HPV infection was attributable to past, not current, sexual behavior at older ages supports a natural history model of viral latency and reactivation. As the more highly exposed baby-boomer generation of women with sexual debut after the sexual revolution transition to menopause, the implications of HPV reactivation at older ages on cervical cancer risk and screening recommendations should be carefully evaluated.