In 12 hospitalized patients with hypertension, clonidine 3 times a day led to better control of blood pressure than did the same total dose administered once daily. Compared to the uniform control of blood pressure on divided dose regimen, the single daily 8 P.M. dose led to wider fluctuations and inadequate control 18 hr after dosing. However, 10 of the 12 patients preferred the single daily dose at 8:00 P.M. to the divided dose regimen because of no drowsiness during the day. In 2 patients administration of clonidine twice daily resulted in better control of blood pressure than that during the single or thrice-daily dose regimens. Since there appeared to be a correlation between the dose and the duration of adequate blood pressure control, administration of clonidine twice a day with a larger dose at bedtime and a smaller dose before noon could limit unwanted drowsiness and combine the convenience of less frequent dosing with superior blood pressure control.