Objective: The superficial femoral popliteal vein (SFPV) has been used as an alternative conduit for both arterial and venous reconstructive surgery. Its popularity continues to grow, despite concern about the potential for venous morbidity after harvest. The purpose of this study was to determine an anatomic 'safe' length of SFPV for harvest, assuming that the preservation of at least one valve and one significant collateral vein in the remaining popliteal vein (PV) segment can minimize venous morbidity. Methods: Forty-four SFPVs were harvested from 39 cadaveric specimens. The length of both the superficial femoral vein (SFV) and PV was measured, and the number and location of valves and significant side branches (more than 2 mm in diameter) of the PV were measured. The Student two-tailed t test was used as a means of comparing vein lengths between the sexes. Correlation coefficients were determined for the effect of patient height on vein length, stratified by means of sex. Results: Vein length (SFV mean, 24.4 ± 4 cm; PV mean, 18.8 ± 4 cm) varied with sex (male SFV mean, 28.1 ± 5 cm; male PV mean, 21.5 ± 3 cm; female SFV mean, 22.6 ± 4 cm; female PV mean, 18.4 ± 3 cm; P = .01). Valve number (mean, 1.8 ± 0.5) and location and collateral vein number (mean, 5 ± 1.8) and location were variable and independent of height or sex. Conclusion: An anatomic 'safe' length of SFPV for harvest to minimize venous morbidity would include all the SFV and 12 cm of PV in 95% of women and 15 cm of PV in 95% of men. We found that the male sex was a significant determinant for a longer safe length of vein that can be harvested.