We evaluated the long-term therapy with Isosorbide Dinitrate Ointment (ISDN-O): 300 mg daily on the painful leg area in 20 male patients (pts) affected by Intermittent Claudication. The efficacy of the treatment was assessed on the basis of the subjective evaluation of pain threshold (daily diary) and objectively by repeated treadmill stress tests performed by each patient at a constant speed, selected according to the severity of symptoms, and by the evaluation of changes both of the distance walked without symptoms (DWS) and of the maximal distance reached (MDR). The maximal duration of the test was 15 minutes independently from the speed. The reproducibility of treadmill tests and the acute effect of isosorbide dinitrate ointment administration were preliminarly evaluated in 2 groups of 5 patients each. The distance walked without symptoms and maximal distance reached in two control stress tests performed in two successive days were: distance walked without symptoms 37 +/- 29 vs 36 +/- 22 m (NS) and maximal distance reached 97 +/- 40 vs 98 +/- 37 m (NS). During the control period and 1 hour after the drug administration distance walked without symptoms was 34 +/- 31 vs 43 +/- 50 m (NS) and maximal distance reached 89 +/- 53 vs 97 +/- 57, (NS) respectively. In a group of 5 patients the effect of one month administration of placebo was evaluated: distance walked without symptoms was m 68 +/- 29 and m 104 +/- 62 and maximal distance reached was m 156 +/- 103 and m 188 +/- 97 basally and after 1 month of placebo (NS).(ABSTRACT TRUNCATED AT 250 WORDS)