Among the cool season legume crops, lentil production has displayed the greatest increase, while cropping of many other grain legumes is actually in decline. This increase is most likely due to a convenient fast cooking coupled to a saving of fuel and time -dehulled lentils cook even faster than milled rice. Worldwide lentil consumption has augmented more than twice the rate of human population growth, with lentil consumption over the past 40 years having increased more than any other food crop. Therefore, continued genetic improvement of lentil is essential in all production regions; nevertheless, without access to and use of diverse germplasm, prospects for yield genetic gain in lentil may be diffi cult to accomplish. Wild Lens accessions represent less than 1 % of the world germplasm collection of this genus, this small fraction likely representing the greatest untapped pool of genetic variation in lentil. Germplasm evaluation together with a successful and targeted hybridization allows for an effi cient breeding and selection of varieties adapted to specifi c environments. The aim of the present chapter is to describe the evolutionary aspects of lentil and assess the gene pool and fl ow for crop improvement, considering levels of diversity and agronomic traits of importance, with emphasis placed on wild species and interspecifi c Lens hybridization, to fi nally conclude with molecular aspects and future prospects of lentil breeding.