There are six Modern South Arabian languages spoken in Oman and in Yemen, but Mehri and Hobyot are the only ones to be spoken together in the two countries : in the East of Yemen and in Western Oman. The Hobyot area is on each side of the border. Mehri is the best documented language while Hobyot, never described, is very little explored, its Omani variety is practically unknown. There is emergency to describe these endangered languages. The aim of this communication is to highlight the wealth of the linguistic patrimony common to Oman and Yemen. There are two parts the first concerning mehri and the second Hobyot. After a brief survey on the native speakers, the research on their language, its dialectology, and the linguistic situation, the main features of phonology, morphology, syntax and vocabulary are pointed out. The purpose is to show similarities and differences between the two languages and the results of the language contact. The data concerning Mehri and Hobyot in Yemen were collected during my fieldworks in the Mahra governorate. As for Mehri spoken in Oman they are essentially based on Johnstone publications.