A 300‐µg oral dose of clonidine was administered to 5 normal volunteers and measurements of plasma concentration and effects upon blood pressure, heart rate, circulatory reflexes, sedation, and dry mouth were made for the following 8 hr. The plasma concentration rose to a peak of 1.02 ± 0.52 ng/ml (SD) at 90 min andfell with a mean half‐life of 12.7 hr. Blood pressure of the group fell from 111.0/77.0 to 87.2/60.4 after 3 hr and was 95.2/62.2 mm Hg at 8 hr. Heart rate in recumbency was slowed. Marked sedation and a fall in sativary flow followed the same time‐course as the plasma concentration. The cold pressor response was reduced but the Valsalva overshoot was tiftle affected.