Background: Given the established links among young age at first intercourse (AFI), number of sex partners, high-risk human papillomavirus infection, and squamous cell cervical cancer (SCC), we hypothesized that women diagnosed with SCC at younger ages would be more likely to report young AFI than women diagnosed later in life. Methods: We performed a population-based investigation among invasive SCC cases who were diagnosed between 1986 and 2004, were ages 22 to 53 years, and lived in the metropolitan Seattle-Puget Sound region (n = 333). Using multivariate linear regression, we estimated coefficients and 95% confidence intervals (95% CI) to assess the association between age at SCC diagnosis and AFI (<15, 15-18, z19 years) and number of sex partners at age <20 years (0, 1, 2-4, 5-14, z15), accounting for birth year and other factors. Interactions were assessed using the likelihood ratio test.