In India, Maize (Zea mays L.) ranks fourth next to rice, wheat and sorghum. In spite of its maximum share in area, the relative contribution is much lower mainly due to extremes of water availability. Evolving varieties tolerant to drought offers low cost technology and is one of the most efficient methods of reducing crop loss, stabilizing the production and economic returns. An understanding of genetic architecture of such traits will enable the breeder to formulate efficient breeding strategies, which aids in evolving varieties tolerant to drought on sound genetic background. The monograph on genetic investigations on maize explains production of single cross hybrids, their evaluation, estimation of general and specific combining ability variances and effects, gene action and kinds of heterosis of hybrids for yield and morpho-physiological parameters under water stress.