The advent and advancement of molecular marker technology has greatly facilitated the identification of quantitative trait loci (QTLs) and their utility in cotton breeding through marker-assisted selection and genomic selection. Since 1998, numerous QTL studies have been performed, with an exponential increase in the number of QTLs reported over the years from 2873 from 92 publications in 2014 to 4982 from 156 publications in 2017 to more than 12,000 from more than 300 publications in 2024. It is a daunting task to perform a manual summary of QTLs for different traits without the aid of a meta-analysis software. A specialized cotton QTL database ( http://www2.cottonqtldb.org:8081 ) based on meta-analysis and a general database ( www.cottongen.org ) for cotton genetics, genomics, and breeding were established for search and comparison of QTLs for various traits. Several meta-analyses have been published to identify consistent QTLs (meta-QTLs) across mapping populations and environments for the same traits and QTL clusters (hotspots) for different traits. With the genome sequencing of different cotton species and resequencing of numerous germplasm accessions in cultivated tetraploid cotton, the identification of candidate genes for different QTLs has become the reality, especially when population sizes and resequencing-based SNP markers are greatly increased. Coupling with RNA-seq, virus induced gene silencing, and gene editing, pinpointing an underlying candidate gene to a QTL has become possible. This chapter briefly reviews the current status of QTL mapping using biparental linkage analysis with a focus on fiber quality and yield traits in cotton.