Benzodioxan has been recommended for the differential diagnosis of hypertension. When given to a patient in whom elevation of blood pressure is due to the release of epinephrine, the adrenolytic properties of the drug are reported to cause a definite and sustained fall in blood pressure.1 Administration of benzodioxan to the patient reported in this article was followed by a rise in blood pressure and precipitation of a typical attack of hypertensive encephalopathy. The circumstances suggested that the attack resulted from the sympathomimetic action of the drug in a susceptible person. Review of the available literature1 and communication with the manufacturer have not disclosed previous instances of such a reaction, although elevation of blood pressure, headache and dizziness have been observed. REPORT OF CASE The patient, O. S., was a short, plump and pleasant 55 year old housewife. She had had paroxysms of dizziness and blurred vision for three