Most agronomic traits are governed by quantitative trait loci (QTLs) and exhibit continuous distribution in a segregating population. The hereditary characteristics of these traits are more complicated than those of monogenic traits. Detection and isolation of these QTLs can greatly improve crop production throughout the world. In recent times, significant progress has been made toward understanding the molecular basis underlying quantitative traits. Herein, we describe a QTL-mapping protocol for detecting and cloning a major QTL regulating rice shoot K(+) concentration under salt stress conditions. This QTL-mapping approach combined with the marker-assisted selection technique can be applied for the elucidation of complex traits in rice and other cereal crops.