Perhexiline maleate was used as a prophylactic agent in 26 patients suffering from severe angina pectoris. The mean duration of treatment was 8.9 months, with a maximum of 28 months. Fifteen patients experienced a reduction in frequency of attacks to less than one-third of their previous level; six experienced a reduction to two-thirds of their previous level; no patient showed an increase in attack rates. During the period of study, there was one death. Frequently observed side effects included dizziness, gastrointestinal irritation and malaise. One patient developed clinically apparent hepatic dysfunction which resolved on withdrawal of perhexiline maleate, but recurred after rechallenge with a lower dose of the drug; the results of liver function tests in five others showed mild abnormalities. One patient developed peripheral neuropathy after taking perhexiline maleate for 18 months, but this resolved in two months after cessation of therapy. Good responses to perhexiline maleate were observed in patients who were concurrently treated with beta-adrenoreceptor blocking drugs.