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