Millet and cowpea crops are important for food security, poverty alleviation and malnutrition in the arid Sahel. The two crops generally grow together and have the advantage of supporting poor climatic conditions such as drought and low use of inputs which characterize agriculture in the world's least developed countries. Recent climate change raised up the dryness phenomenon and the traditional species cycle of production is no longer adapted to the reduced length of the wet seasons. New early and drought tolerant varieties are needed to ensure a steady supply of food in the driest regions on the planet. As it was done in numerous species, the mutation induced breeding can help to develop new crop varieties in pearl millet and cowpea. This method is carried out in Niger, in the Laboratory of Plant Breeding and Biotechnology to find out varieties of pearl millet and cowpea, more drought and high temperatures tolerant. This work examines the sensitivity of these two species to gamma radiation, as a first prerequisite step, for crop improving using mutation induction technique. The LD50 was found to be 669,3 Gy for millet crop and respectively 176,6 and 209,4 Gy for TN578 and IT90K 372-1-2 cowpea varieties.