Endoscopic saphenous vein harvesting (ESVH) requires a high degree of technical expertise. However, few studies have investigated the influence of SV caliber on the technical difficulty and outcome of ESVH. We analyzed 86 consecutive patients who underwent ESVH using a VirtuoSaph(trade mark) system. SV caliber was measured in the above-knee portion by ultrasound. Patients were then divided into two groups: group A (SV caliber <3 mm, n=16), and group B (the remaining patients, n=70). ESVH procedure time and SV characteristics were compared between the groups. In group A, the SV had a larger number of side branches (11.7+/-1.2 in A, 9.8+/-0.4 in B, P=0.043) and required a longer operation time (A, 57.5+/-3.7 min; B, 43.9+/-1.9 min, P=0.0024), whereas the time required for endoscopy did not differ. Graft length (A, 27.7+/-5.0 cm; B, 25.7+/-3.7 cm) and ratio of repaired side branches (A, 26.6+/-20.5%; B, 25.7+/-23.9%) showed no significant differences. ESVH using a VirtuoSaph(trade mark) system is feasible, regardless of SV caliber. SV with a caliber of <3 mm has a larger number of side branches, thus prolonging the procedure time.