Evapotranspiration (ET)is a major component of surface water balance over land and thus plays a key role in drought development and for long-term drought changes. Global warming is expected to increase evaporative demand for mositure and leads to drier conditions over many land areas. In this presentation, I will review some of the key issues and challenges in assessing historical and future changes in ET and drought, including large uncertainties in estimating historical changes in land precipiaiton, radiation, humidity and wind speed, and how these uncertainties affect our estimated changes in global ET and drought. Finally, a few thoughts on model predicted changes in ET and drought will be discussed.