A single-blind, prospective, crossover study of 27 ambulatory hypertensive outpatients was conducted to compare the antihypertensive effects of single daily dose versus multiple daily dose methyldopa regimens. Patients were randomly assigned to the two treatment modalities for a four-week study period. After four weeks patients were crossed over to the other study regimen. Each patient's blood pressure was determined three times daily, once each week. At the end of the study both treatment modalities were equally effective in controlling blood pressure levels. No serious adverse reactions were detected. This study has shown that patients currently on divided daily doses of methyldopa can be effectively treated on a single total dose of the medication.