Chiral recognition of d- and l-amino acids is achieved and mixtures of enantiomers quantified in the gas phase, using the kinetics of competitive unimolecular fragmentations of trimeric Cu(II)-bound complexes. Singly charged copper(II)−amino acid cluster ions [CuII(A)(ref*)2−H]+ (A = amino acid; ref* = chiral reference ligand, selected from among the natural α-amino acids) undergo competitive collision-induced dissociation (CID) in a quadrupole ion trap to form the dimeric complexes [CuII(A)(ref*)−H]+ and [CuII(ref*)2−H]+. The abundance ratio of these fragment ions depends strongly on the stereochemistry of the ligands in the precursor [CuII(A)(ref*)2−H]+ complex ion and specifically on the chirality of the analyte amino acid. The chiral selectivity, the ratio of the two fragment ion abundances for the complex containing one enantiomer of analyte expressed relative to that for the fragments of the corresponding complex containing the other enantiomer, ranges from 0.47 to 11. An energy quantity, Δ(ΔCuIIBDE...