Cetirizine dihydrochloride (CTZ), an antihistamine, forms two 1:1 inclusion complexes with β-cyclodextrin (β-CD) in aqueous solution as confirmed by detailed1H NMR, COSY and ROESY spectroscopic studies. The stoichiometry and overall binding constant of the complexes were determined by the treatment of1H NMR chemical shift change (Δδ) data. Most of the CTZ protons exhibited splitting in the presence of β-CD.