Lentil (Lens culinaris Medikus) is an important cool season legume, particularly within countries in North America, South Asia, West Asia, and North Africa (Erskine et al. 2009). The seeds are a cheap source of protein with a high vitamin and mineral content, thus contributing to alleviation of hidden hunger. However, lentil yields are generally low. Lentil is commonly grown in developing countries on marginal lands with poor soil in rainfed environments (Gahoonia et al. 2006). Like many other crops that grow in Mediterranean and semiarid climates, lentil often faces terminal drought stress during the reproductive phase as a consequence of diminishing rainfall or plant available water and rising temperatures. In such cases, what is usually called "drought tolerance" could be, in part, the consequence of plant constitutive traits that affect how soil water is used when water is non-limiting to plant transpiration (Vadez et al. 2014). Until recently, the two water-conservation traits considered in this book have been missing in lentil drought studies, so this chapter mainly reports research that is currently underway. In lentil, experiments conducted in Western Australia, with a Mediterranean-type climate, showed that seed yield was not correlated with total water use or with water use before flowering (Leport et al. 1998), but was positively correlated with post-flowering water use (Siddique et al. 2001). Under rainfed environments in Nepal and Jordan, early-sown lentils produced greater yield as a result of adequate vegetative mass, longer grain-filling periods, and higher pod number (Neupane and Shrestha 1991; Shrestha 1996; Rahman et al. 2002). It is, however, surprising that these findings on seasonal dynamics of water use has not been investigated any further in lentil as to whether there is early-season soil water conservation so that more water is available to complete seed filling under drought conditions, occurring late in the growing season (Ludlow and Muchow 1990; Sinclair et al. 2005).