Analysis by GC-MS/MS showed that a worldwide collection of 58 wheat accessions differed significantly in the amounts of 7 known phenolic acids exuded by the living roots of 17-day-old wheat seedlings. The quantities of exuded allelochemicals varied with the specific compound and ranged from 2.3 to 18.6, from 0.6 to 17.5, from 0.1 to 4.9, from 0.0 to 52.7, from 0.33 to 12.7, from 1.5 to 20.5, and from 1.6 to 23.4 Ãg/L of water/agar for p-hydroxybenzoic, vanillic, cis-p-coumaric, syringic, cis-ferulic, trans-p-coumaric, and trans-ferulic acids, respectively. The concentrations of p-hydroxybenzoic and vanillic acids exuded by wheat seedlings were normally distributed in the 58 accessions. The level of each phenolic acid in root exudates did not correlate well to that previously observed in wheat. In comparison with weakly allelopathic accessions, strongly allelopathic accessions exuded larger quantities of allelochemicals into the growth medium. The chemical basis for wheat seedling allelopathy is an area for further investigation.