Sponsored by the Structural Engineering Institute of ASCE This report describes an investigation into nearly 500 roof collapses and snow-related roof problems that occurred in the northeastern United States during the winter of 2010.2011. The key issue is whether the collapses and poor roof performance were the result of snow loads exceeding what was prescribed in building codes or of structural capacity that was significantly less than required by the building codes. Weather data from Connecticut, Massachusetts, New York, and Rhode Island is examined, along with case studies of snow-related roof problems derived from databases of three states and five engineering firms. The ground snow loads set out in ASCE 7, Minimum Design Loads for Buildings and Other Structures, are summarized and assessed in comparison with actual ground snow loads. The nominally uniform roof snow loads recommended in ASCE 7 are evaluated in case studies and compared for heated and unheated structures. Drift loads from ASCE 7 are also described and evaluated for leeward roof step drifts, gable roof drifts, and snow flux. Appendixes present weather data tables, case study databases, and drift load calculation tables. The analysis and findings in this report are important to structural engineers, architects, building code officials, owners, and construction professionals working in areas subject to significant snowfall.