The oxidation of small oligothiophenes and oligopyrroles (bipyrroles) has been investigated by pulse radiolysis in aqueous solutions containing hydroxypropyl-beta-cyclodextrin. Oxidation by the N-3(.), Cl-2(.-), or Br-2(.-) radicals produces the corresponding radical cations, which are identical to those observed in organic solvent. Detailed kinetic studies with methylbipyrrole show that the homogeneous oxidation occurs after dissociation of the complex but also with the complex itself, contrarily to what is commonly described for electrochemical reduction or oxidation. The produced cation radical is not associated with the cylodextrin and is rapidly expelled from the host after its formation. On the contrary, if the cation radical is deprotonated to form the neutral radical, the neutral radical is associated with the cyclodextrin. Dissociation kinetics rate constants were found to be fast for both cation radical and neutral radical.