Emergency department (ED) visit volumes are increasing nationwide. To determine whether states with primary care shortages have higher rates of ED use. Populations residing in primary care shortage areas were abstracted from the Health Resources and Services Administration Geospatial Database. Annual ED visit volumes were available from the 2001 National ED Inventory. Population data and potential confounders were abstracted from federal data sets. All analyses were conducted at the state level. Primary care shortage densities varied greatly across states, ranging from 3 (New Jersey) to 28 (Mississippi) medically underserved individuals per 100 people. States also varied in their annual ED visit densities, ranging from 23 visits (Hawaii) to 65 visits (Washington, DC) per 100 people. Of the 17 states in the top tertile for primary care shortage, 7 also were in the top tertile for ED visits. Primary care shortage density was positively associated with ED visit density. An increase of 10 medically underserved individuals per 100 people was associated with an annual increase of 4.2 ED visits per 100 people (p = 0.04). The association remained after controlling for six factors, with an increase of 10 medically underserved individuals per 100 people associated with an annual increase of 3.3 ED visits per 100 people (p = 0.04). Nevertheless, five states had high ED visit densities despite comparatively low primary care shortage densities (Maine, Massachusetts, New Hampshire, Rhode Island, and Vermont), whereas five others had low ED visit densities despite high primary care shortage densities (Arizona, Idaho, Montana, New Mexico, and South Dakota). A positive association between primary care shortage densities and ED visit densities was found. Although most states adhere to this pattern, some states do not. Further investigation of this dissociation may yield additional explanations for rising ED visit volumes.