Varicose veins alternate areas of phlebosclerosis and hypertrophy of the vein wall. In this study, samples of long saphenous veins obtained from patients submitted for aortocoronary saphenous vein graft or for surgical resection of varicose saphenous veins were examined. Histologic changes in the intima, muscle, and adventitial layers were quantified. Thicknesses of the venous wall layers were obtained by linear measurements, and the volumetric density of the connective tissue in the muscle layer was determined by point counting. The muscle layer thickness was 300 +/- 13 and 581 +/- 25 microns in normal and varicose veins, respectively. A more severe connective tissue accumulation within the muscle bundles was found in the varicose condition. The volumetric density of the connective tissue in the circular muscle layer (CmC/MmC) showed also a marked difference between varicose (0.67 +/- 0.08) and normal veins (0.43 +/- 0.02), P < 0.05. The authors suggest that the varicose condition is associated with a connective tissue uniform accumulation among muscle cells in the circular muscle layer.