New crystal structure maps have been proposed on the basis of the molecular orbital calculations of electronic structures. Two electronic parameters have been introduced and employed as new parameters for the classification of crystal structures. One is the bond order and the other is the d-orbital energy level of elements. Both of them change following the position of elements in the periodic table. With these parameters crystal structure maps have been constructed for aluminides, silicides, and some transition-metal-based compounds. There is a clear separation of the crystal structures on the maps. These maps are found to be applicable to the prediction of crystal structures not only for binary compounds but also for ternary compounds. The possibilities of structural modification of and by alloying are also discussed with the aid of these maps.