Petrographic and electron microprobe mineral analyses of pastes and paints of seventeen samples of various ceramic ware types from Tepe Yahya, Iran, indicate that most of the abundant red, buff and coarse chaff-rich sherds were made at the site. This conclusion is supported by the local geology. The mineral assemblage and firing technology of the fine gray wares show they were probably imported, but manufactured at a single site. The single Ubaid-style piece appears to have been brought in from southern Mesopotamia. The combination of Western design elements with a local origin of most of the Period VB buff ware indicates that the styles were diffused and not the wares. This fact, along with others from this preliminary study, helps to clarify the processes of technological development and cultural contact in Iran between 5000 and 3000 B.C.