Maize (Zea mays L.) is one of the most important and versatile agricultural crops used as a staple food by several hundred million people in the developing world. It is an important crop for countries like Pakistan where the rapidly increasing population demand increased food supplies. Being a short duration crop it gives two crops (spring and autumn maize) per year in Pakistan and can help considerably to solve the food shortage problem. It can act as alternate food source when the conventional cereal grains i.e. wheat and rice are deficient. Maize ranks 3rd most grown crop in the world with an area of178.69 million hectare and annual production of 1,008.99 million metric tons (USDA-FAS, 2017). In Pakistan maize is the 4th largest grown crop after wheat, cotton and rice. The area under maize in Pakistan is about1.14 million hectares with about 4920 thousand tones production and 4301 kg ha-1 average yield (PBS 2017). More than 90% of the total production of maize in Pakistan comes from two provinces, Khyber Pakhtunkhwa and Punjab. About 39 per cent of the total area under maize and 30 per cent of total production is contributed by Punjab; Khyber Pakhtunkhwa contributes 56 per cent of the total area and 63 per cent of the production while five per cent of the total area and three per cent of the total production is contributed by Sindh and Baluchistan. In spite of potentially high yielding and easily cultivated crop than any other cereal, maize production in Pakistan is still low as compared to other important maize growing countries of the world. With the use of high yielding varieties/genotypes, maize production can certainly be improved. It is therefore imperative for the maize breeders to develop maize varieties that are high yielding, widely adopted, early maturing, disease resistant, responsive to improved production practices and adjustable in the existing cropping pattern. In the past, breeders around the world used procedures for seed production including mass selection wherein seeds from good ears or plants were selected and saved each year for next year sowing and hence produced some widely used cultivars (Kutka, 2011). The deterioration in yield potential of these cultivars with the passage of time made it essential to develop and select improved modern cultivars/hybrids that are high in grain yield and accompanied with superior quality. This lead to the development of modern maize hybrids that have greater potential as compared with older cultivars/hybrids and hence corn became the highest tonnage cereal crop worldwide (Troyer and Wellin, 2009). The methods for the generation of hybrid seed and up keep of parental lines are all well archived. Several studies involving the development and release of maize hybrids have been focused significantly by the scientific community. However, less attention has been paid on the development, maintenance, and multiplication of hybrids derived from improved maize populations. Maize populations like composites, gene pools, and advanced generations of varietal crosses, etc. are routinely developed by crossing genetically diverse maize genotypes which are then improved through recurrent selection. A specific combination from the improved population can be released as an improved OPV or population hybrid for cultivation. In spite of the fact that these population hybrids are not essentially uniform in agronomic attributes when contrasted with innate inbred hybrid yet these can be acquired with significant decrease in time and resources and great yield than OPVs. It is relatively uniform and stable over time for important agronomic traits in its area of adaptation than inbred hybrids. If produced by crossing selected populations of similar maturity, plant and ear height, and other morphological traits, a population hybrid will be more uniform, more acceptable to farmers, and easier to maintain and produce seed for. Therefore, promising populations once identified can be elite sources of new inbred lines and population hybrids. Properly selected hybrids between populations could be used for commercial seed production (East and Hayes, 1911). The crosses could also provide unrelated and diverse elite inbreds with good GCA/SCA to be used in conventional hybrid seed industry. Inbred lines developed from such broad-based populations also carry the advantage of having good combining ability with lines derived from more than one heterotic group (Carena, 2005). Evaluation of early generation inbred progenies in test crosses has been the primary method used in maize breeding. For superior genotypes identification, visual selection of S2 lines offers greater opportunity for early generation testing. Information on combining ability and heterotic grouping for newly developed inbred lines is of paramount importance to design future breeding strategies for the development of hybrid and synthetic varieties. Proper selection of parental lines is therefore very important step in the development of hybrids in breeding program (Lippman and Zamir, 2007). Heterosis and combining ability is pre-requisite for developing a desirable maize hybrid that are economically viable, used as a commercial maize hybrid variety. Heterosis responses of newly developed hybrids largely depend on genetic diversity present among parental lines and increases with increased genetic diversity (Rauf et al., 2012). Crossing promising population and testing the early selfing generations in line × tester combination can therefore provide a good source of elite inbred lines. Based on these facts, the current study was therefore conducted for the development and identification of improved maize population hybrids with the following specific objectives to; • Compare grain yield and agronomic performance of maize population hybrids with check(s) and identify superior combination(s) for commercial use as cheaper hybrids. • Estimate heterosis in population hybrids obtained from diallel crosses of improved populations. • Estimate combining abilities of new inbred lines of the crosses for grain yield and other morphological traits using line × tester mating for future maize breeding programs. • Enrich the available maize gene pool by crossing diverse maize populations, thus enhancing the maize genetic diversity in reserve.