A n adequate and appropriately trained physician workforce is necessary to meet the nation's current and future health care demands. As the US population continues to increase and age, there is an unmet need for dermatologic care. 1 The increasing incidence of skin cancer, high prevalence of complex inflammatory skin disorders, advanced therapeutics, and widening market for surgical and noninvasive procedures have also contributed to an increased demand for dermatologists that is expected to continue to increase. 1-7 The undersupply of dermatologists has been described during the past 2 decades, 5,8-10 and previous work has identified the maldistribution of physicians and dermatologists. 11-14 Rural areas face significant physician workforce shortages, with rural residents experiencing long wait times and traveling long distances to receive care. 5 This pattern is especially important given previous studies 15-17 that found that dermatologist density is associated with patient outcomes for diseases, such as melanoma and Merkel cell carcinoma. To develop strategies and effective policies to offset a shortage, we must better understand the characteristics and patterns observed in the dermatologist workforce. We hypothesize that despite an expanding dermatologist workforce, there is a widening gap between dermatologists in urban and rural settings given the greater professional opportunities in urban areas, desire for proximity to family and support, and insufficient financial incentives to practice in resource-poor areas. 13,18-22 The goal of this study was to build on existing work by evaluating the up-to-date longitudinal trends and demographic and environmental factors associated with the geographic distribution of dermatologists, using a classification scheme that measures the degree of urbanization in each US county. Methods Demographic and physician data from 1995 to 2013 were obtained from the Area Health Resources File (AHRF). 23 The New IMPORTANCE As the US population continues to increase and age, there is an unmet need for dermatologic care; therefore, it is important to identify and understand the characteristics and patterns of the dermatologist workforce. OBJECTIVE To analyze the longitudinal dermatologist density and urban-rural disparities using a standardized classification scheme. DESIGN, SETTING, AND PARTICIPANTS This study analyzed county-level data for 1995 to 2013 from the Area Health Resources File to evaluate the longitudinal trends and demographic and environmental factors associated with the geographic distribution of dermatologists. MAIN OUTCOMES AND MEASURES Active US dermatologist and physician density. RESULTS In this study of nationwide data on dermatologists, dermatologist density increased by 21% from 3.02 per 100 000 people to 3.65 per 100 000 people from 1995 to 2013; the gap between the density of dermatologists in urban and other areas increased from 2.63 to 3.06 in nonmetropolitan areas and from 3.41 to 4.03 in rural areas. The ratio of dermatologists older than 55 years to you...