The effects of acetylandromedol alone and in combination with 2-(2,6-dichlorophenolamino)-2-imidazoline hydrochloride (clonidine) on the arterial blood pressure and the preganglionic discharges of the cervical sympathetic and phrenic nerves were studied in 36 anaesthetized cats. At a dosage of 10--40 micrograms/kg i.v. acetylandromedol produced a fall of blood pressure and an increase of the central nervous sympathetic activity. Both effects lasted longer than 1 h. The combination of 40 micrograms acetylandromedol/kg with 15 micrograms clonidine/kg i.v. caused a decrease of the sympathetic activity. A depression of the respiratory centres was not observed. 10 micrograms acetylandromedol/kg in combination with 15 micrograms clonidine/kg produced a significantly more pronounced hypotensive action than the single application of 20 micrograms acetylandromedol/kg or 30--120 micrograms clonidine/kg.