This invention relates to a new composition of matter which comprises hydroxybutenyl derivatives of cyclodextrins (HBenCD) or mixed ethers of cyclodextrins where at least one of the ether substituents is hydroxybutenyl (HBenRCD where R is an ether substituent other than hydroxybutenyl). This invention also relates to novel processes for the preparation of cyclodextrin ethers. This invention further relates to inclusion complexes formed between HBenCD or HBenRCD and guest molecules. Such inclusion complexes are useful in pharmaceutical, cosmetic, and food applications. Furthermore, this invention relates to the incorporation of HBenCD or HBenRCD or their inclusion complexes in thermoplastic materials, textiles or membranes.