• Mecamylamine hydrochloride blocks conduction through autonomic ganglions and is presumed to be completely absorbed when given by mouth. It was evaluated in the treatment of 35 patients with severe hypertensive disease. The initial dose was 2.5 mg. given once or twice daily by mouth; subsequent doses were increased by 2.5 mg. every two days up to the individual patient's requirement for maintenance as determined by the standing systolic blood pressure and therapeutic response. The average daily maintenance dose for the 18 patients who responded with a significant reduction of the blood pressure was found to be 24 mg. (range 5 to 45 mg.). There were, however, 17 nonresponders. Of the 35, only one tolerated therapeutic doses without side-effects and 6 had to stop taking the drug. The others, though uncomfortable, were able to continue medication, in some instances, up to 12 months. The most frequent complaints were constipation, blurring of vision, xerostomia, and various symptoms of postural hypotension. Seven patients, including 5 from this group of 35, showed signs of an unusual neuromuscular disorder, with anxiety, tremor, and even convulsions, while taking the drug. Mecamylamine is considered to be a useful agent in the treatment of hypertensive disease. Its therapeutic advantage over drugs with similar ganglionic effects is small.