The anti-anginal properties of single doses of a new anti-hypertensive drug, cicletanine, were investigated in a double-blind, randomised, balanced, crossover comparison with placebo in sixteen patients with chronic stable angina pectoris. All subjects underwent treadmill exercise 2 h after drug administration and 24 h ambulatory ECG monitoring with ST scanning. Although there were significantly fewer episodes of ST depression on ambulatory monitoring after cicletanine, total exercise duration and time to 1 mm ST depression were unchanged. This report provides little evidence of an acute anti-anginal effect of cicletanine but longer term studies may be indicated to further evaluate this drug's potential role in the management of angina pectoris.