ABSTRACT. – Estimating the evapotranspiration is important for many sides. The first is to determine the amount of water really needed by vegetable canopies. The second is to analyse the role of plants in buffering the effects of climatic change. In this work we have tried to evaluate the amount of evapotranspiration inside and above the traditional oasis of Tozeur by monitoring profiles of global radiation, net radiation, sap flow, sensible heat flux, latent heat flux, air temperature and air humidity. We have used fixed captors installed at different heights inside the oasis and mobile captors carried by a meteorological balloon. Resultats show that evapotranspiration deduced from the total global radiation intercepted inside the oasis is equivalent to 4,4 mm/day. That estimated from global radiation received above the oasis is equivalent to 6,81 mm/day. When using the total net radiation intercepted by all the oasis (respectively the net radiation received above the oasis), the evapotranspiration is equivalent to 3,24 mm/day (respectively about 4 mm/day). The evapotranspiration estimated from daily sap flow transpired is about 3,3 mm/day. We have noticed also, that inside the oasis air temperature follows a decreasing function with the altitude in the early morning and later in the afternoon. It follows an increasing function between 9 and 15 hours. Above the oasis, air temperature, relative humidity and air pressure, follow globally decreasing functions with altitudes. However, considerable levels of fluctuation were recorded for all the parameters throughout the first altitudes above the oasis.