In a double-blind crossover study, it has been shown that the hypotensive response to propranolol in 24 patients with essential hypertension was no greater at doses of 80, 160, or 240 mg twice daily than at 40 mg twice daily. A relationship was observed between dose and response as defined by the ability to achieve a standing diastolic blood pressure of 95 mm Hg. Four patients with low plasma renin activity (PRA) had no fall in blood pressure even at highest dose levels. Plasma propranolol levels in the groups were related to dose, and up to a concentration of 300 ng/ml, with degree of beta-adrenoceptor blockade; there was, however, no correlation with hypotensive response.