Various species of Acacia and Prosopis are considered as most suitable for hot deserts of Pakistan. In order to evaluate the performance of 24 species and seed sources of these genii, 2 field trials were established one each under arid and semi-arid conditions following RCB and single tree plot designs. The height growth data of indigenous species were compared with exotics. Preliminary results have shown that under arid and semi-arid conditions (rainfall between 300-900 mm per annum) exotic species like Prosopis chilensis, P. alba and P. pallida exhibited 1 and half to 3 times better growth than P. cineraria indicating the scope of improvement of exotic Prosopis species on marginal and low nutrient lands in the country including saline and waterlogged areas. Large scale planting of these species is therefore, recommended in the country.