Because most expression quantitative trait locus (eQTL) studies measure the steady-state level of mRNAs, they cannot distinguish between changes in transcript production and decay rates. Pai et al. measured mRNA decay from 16,000 genes in 70 Yoruban HapMap lymphoblastoid cell lines. For 10% of genes, steady-state expression levels correlated with variation in decay rate variation, and 195 loci — dubbed RNA decay quantitative trait loci (RdQTLs) — were identified as being associated with this variation.