Selection procedures used in plant breeding have gradually developed over avery long time span, in fact since settled agriculture was first undertaken.Nowadays these procedures range from very simple mass selection methods,sometimes applied in an ineffective way, to indirect trait selection based onmolecular markers. The procedures differ in costs as well as in genetic effi-ciency. In contrast to the genetic efficiency, costs depend on the local conditionsencountered by the breeder. The genetic progress per unit of money investedvaries consequently from site to site. This book considers consequently onlythe genetic efficiency,i.e.the rate of progress to be expected when applyinga certain selection procedure.