Abstract: The dissolution of lipophilic compounds in aqueous solutions of hydroxypropylcyclodextrins can be accelerated by the addition of co-solubilizers, such as ethanol or ammonia, which again can be removed, together with water, by evaporation or by freeze-drying leaving lipophile: hydroxypropylcyclodextrin complexes as a residue. The co-solubilizer method was used successfully with steroid drugs (5-androstene-3.beta.,17.beta.-diol, 4-androstene-3,17-dione, dehydroepiandrosterone, dexamethasone, 5-.alpha.-dihydro-testosterone, 6-methylprednisolone, and testosterone), peptides (gramicidin S) and a macrocyclic antibiotic (amphotericin B). The complexes prepared in this manner were amorphous and possessed satisfactory stability.