Is the urban UVB environment in the Baltimore area different from rural locations? The Baltimore Ecosystem Study (BES LTER site) Solar Radiation Monitoring Station began recording hourly averages of broadband UVB radiation, photosynthetically active radiation, and total solar radiation in May 2001 in part to help answer this question. The May through August radiation measurements are compared to weather conditions and measurements made at two USDA UVB Monitoring Program stations at Queenstown (67 km SE) and Beltsville MD (46 km SSE) to evaluate the differences in the urban and rural radiation environment. The UVB irradiance at Baltimore was more similar to that at Beltsville in the Washington-Baltimore metropolitan area than Queenstown across the Chesapeake Bay. The mean difference in daily UVB dose between the Baltimore and Beltsville sites was less (only 0.3 KJm-2 ) than that between Baltimore and Queenstown (2.1 KJm-2 ). Daily variability was greater between Baltimore and Queenstown than between Baltimore and Beltsville. The greatest difference in daily dose between Baltimore and Beltsville occurred when the winds were from the east or the air was nearly stagnant over the region. The daily UVB dose at Queenstown was largely dependent on the aerosol optical thickness and not ozone column depth, indicative of other rural UVB monitoring locations. The daily UVB dose at Beltsville was uncorrelated with either aerosol optical thickness or ozone column depth. These conditions may be characteristic of urban locations. Extreme UVB irradiance differences between locations will be discussed in light of the weather conditions and atmospheric composition.