The Ra's al-Hamra prehistoric fishermen lived in isolation on the Qurum rocky promontorium in Oman during the 5th-4th millennia BC. To date, they represent the most ancient and numerous human fossil group excavated from the Arabian peninsula. Like other contemporaneous archaeologically documented small communities along the desert Arabian coasts, they intensively exploited ocean resources and collected molluscs from nearby mangrove swamps. The present study analyzes aspects of dental anthropology (including crown variation, morphology, dental wear, and oral health), in 600 permanent teeth from 49 individuals of both sexes excavated at the Mesolithic RH5-site by the Italian Archaeological Mission in Oman from 1981 to 1985. In association with a general low degree of morphometric variation, the Ra's al-Hamra dental crowns show low sexual dimorphism and are consistently reduced in size. These features are unexpected in a preagricultural population, especially when these data are compared to other eastern African and near Middle Eastern prehistoric populations. These data are discussed within the general context of human dental structural reduction occurring during the post-Pleistocene and are interpreted according to the "increasing population density effect" model. There are other significant differences that characterize the Ra's al-Hamra dentitions with respect to both eastern and western prehistoric human groups. The frequency of numerous nonmetric crown traits supports the hypothesis that a microdifferentiation phenomenon occurred in this marginal area. The preliminary skeletal analysis and the palaeodemographic profile show that the Omani prehistoric fishermen were affected by genetic isolation and inbreeding as well as strong environmental stress. Because of the grit assimilated with dried fish and the high shellfish consumption, dental wear was extreme in all age groups at Ra's al-Hamra and occasionally was responsible for serious hematogenously spread infections. In spite of the great anthropological importance of ancient Arabian populations, very few studies on skeletal and dental samples have been completed. The present paper offers an odontological data set for future comparative research in the area.