Abstract: Genetic variability is an important feature for plant breeding and crop improvement. The amount of variability that exists in the germplasm collections of any crop is the most important towards breeding for better varieties, particularly genetic variability for a given trait is a basic prerequisite for its improvement by systematic breeding. The success of any crop improvement program is not only depend on the amount of genetic variability present in the population but also on the extent to which it is heritable, which sets the limit of progress that can be achieved through selection. Heritability alone provides no indication of the amount of genetic improvement that would result from selection of individual genotypes. Hence knowledge about genetic advance coupled with heritability is most useful. Heritability and genetic advance should be considered simultaneously because it is not always true that high heritability will always be associated with high genetic advances. Further, efficiency of selection in any breeding program mainly depends upon the knowledge of association of traits. For effective selection, information on nature and magnitude of variation in population, association of character with yield and among themselves and the extent of environmental influence on the expression of these characters are necessary. Correlation coefficient and Path coefficient analysis are the most important tools to describe association of traits in maize breeding program.