The haemodynamic effects on the peripheral vascular bed of L-acetylcarnitine, L-propionylcarnitine, and nitroglycerin were tested by echo-Doppler in a double blind cross-over study. Eleven male patients suffering from peripheral arterial obliterative disease (PAOD) in the second stage of Fontaine's classification, and 11 matched control subjects were enrolled in the study. Each subject received one of three different treatments on each day of the study in a different order following a random assignment. The treatments were either 30 mg x kg of L-acetylcarnitine (LAC) or 30 mg x kg of L-propionylcarnitine (LPC) or nitroglycerin (NTG) 1.25 mg given as a single i.v. bolus injected over 3 min. Echo-Doppler measurements of blood flow velocity, and cross-sectional area of the femoral artery were performed at baseline and 10, 20, and 30 min after injection of the drugs. Pulsatility Index (an index derived from the blood flow velocity and related to vascular resistance: PI = Vmax - Vmin/Vmean) was also obtained each time. Results were analysed using a Student's t-test for paired data. L-acetylcarnitine and L-propionylcarnitine showed no haemodynamic effects in either group of subjects (controls and PAOD patients) whether blood flow or vascular resistance was considered. There were haemodynamic changes (a decrease in blood flow velocity and an increase in arterial systemic resistance) only after NTG administration. The changes were more evident in controls than in PAOD patients. Femoral artery cross-sectional area showed no statistically significant effect as regards treatment.(ABSTRACT TRUNCATED AT 250 WORDS)