1. After some exclusions, 169 severe uncomplicated essential hypertensive patients presenting consecutively were divided into two groups according to their treatment. Of these, 121 had been given long-term treatment containing propranolol (PC group) and forty-eight had been treated with hypotensive agents excluding any β-receptor-blocker group, the non-β-receptor-blocker (NBB) group.
2. There were no significant differences in myocardial infarction risk factors between the two groups.
3. After a mean follow-up of 5·25 years, nine of the 121 subjects (7·5%) in the PC group had suffered first infarctions and fifteen of the forty-eight subjects (31%) in the NBB group, a significant difference (P < 0·01).
4. It was concluded that the presence of propranolol had prevented more or caused fewer infarctions, perhaps a combination of both, than had the older hypotensive agents unsupported by β-receptor blockade.