Purpose: Motor vehicle crashes (MVCs) are the leading cause of death for children ages 1-14 years in the United States. Car safety seats are effective in decreasing the risk of injury and death, and rear-facing car safety seats (RFCSSs) are significantly more effective than forward-facing seats in protecting children less than 24 months of age. While the American Academy of Pediatrics (AAP) recommends that children remain in a RFCSS until at least 2 years of age, many families turn their children forward-facing before their second birthday. We examined the prevalence and determinants of RFCSS use in a sample of children 17-19 months of age born at a university hospital. Methods: Participants were caregivers of children born November 2013-May 2014. Participants completed a telephone survey in 2015-2016 focused on car seat knowledge, attitudes, and use. The prevalence and odds of RFCSS use in reference to hypothesized determinants were estimated. Adjusted odds ratios (aOR) and 95% confidence intervals (CI) were calculated using multivariable logistic regression. Results: In total, 56% (491/877) of potentially eligible caregivers completed the survey. Of these, 62% reported RFCSS use for their child. Race, education, rurality and household income were associated with RFCSS use after controlling for potential confounders. Additionally, caregivers who reported having discussed car seats with their child’s health care provider (aOR=1.7; CI=1.1-2.6), received their child’s primary care in pediatrics compared to family practice (aOR=2.4; CI=1.1-2.6) and were aware of the AAP rear-facing recommendation (aOR=2.8; CI=1.8-4.1) were significantly more likely to still be using RFCSSs. Conversely, caregivers who previously used a car seat with another child were less likely to still have their child rear-facing (aOR=0.6; CI=0.4-0.9). Conclusion: Many families surveyed continued to keep their children in RFCSSs through 17-19 months of age. Children cared for by pediatricians were more likely to remain rear-facing than those cared for by family practitioners. Caregivers who were aware of the AAP recommendations and had discussed best-practice RFCSS use with their child’s primary care provider were more likely to remain rear-facing, suggesting that anticipatory guidance and public education remain crucial tools in preventing motor vehicle related injuries. Caregivers who had previous car safety seat experience were more likely to have prematurely turned their child forward-facing, suggesting the need for targeted programs to encourage correct RFCSS use among experienced caregivers.