The 1,2-dimethyl-3,5-diphenyl-pyrazolium cation (the herbicide difenzoquat) forms a weak inclusion complex with beta-clodextrin having the stoichiometry 1:1. The stoichiometry of the complex and the formation constant K = 66 +/- dm3 mol-1 were determined by voltammetry and UV spectroscopy. The reduction product forms a slightly stronger complex than the difenzoquat cation itself. The inclusion of difenzoquat by alpha- and gamma-cyclodextrins is negligible. H-1-NMR data indicate that the guest most probably enters the beta-CD cavity with the pyrazole ring.