There is evidence that significant deterioration in solar collectors used for residential and commercial building applications can occur as a result of exposure to environmental conditions. This problem indicates the need for validated testing and evaluation procedures that can be used to assess the deterioration of solar collectors and their associated materials. A program is being undertaken at the National Bureau of Standards (funded by the Department of Energy) to develop meaningful collector durability/reliability tests. Both laboratory and outdoor field exposure tests will be performed on collectors and collector materials. These tests will take into account the deterioration that can occur at the collector level as a result of exposure to stagnation conditions, thermal shock, moisture, wind, and snow loads, etc. Materials tests in the laboratory or field include ultraviolet (UV) degradation, thermal degradation, and moisture resistance. Correlations will be made between actual and simulated degradation for both collectors and their materials.