50 healthy subjects (25 men and 25 women; age range: 18 to 80 years) have been examined. The internal calibers of the common femoral artery, of the superficial femoral artery, of the common femoral vein, and of the superficial femoral vein have been measured in selected locations using Color Doppler Ultrasonography. The difference in vessel caliber between men and women was statistically significant (p < 0.01). There was no significant difference in left versus right vessel calibers for all the four vessels studied. In the same subject, vessel caliber was directly proportional in the left compared to the right side (p < 0.01). Both in the left and in the right side, arterial and venous calibers of the same subject in the same side were directly proportional (p < 0.01). The relationship between the calibers of the four vessels under study and age, height, and body surface area were not statistically significant.