Stone mastic asphalt (SMA) pavements were first built in the United States in 1991 using technology obtained from Europe. It was determined, however, that significant differences exist in the aggregate properties and mix design methods used. ln addition, differences in the plant production methods and in the laydown and compaction procedures are present. This resulted in a number of problems in constructing the stone mastic asphalt pavements that are discussed. To date, after up to six years of service under traffic, the performance of the SMA pavements has been excellent.