['We investigate the value of vein mapping for predicting the risk of endovenous heat-induced thrombosis (EHIT) after endovenous laser treatment (EVLT) and radiofrequency ablation (RFA) of the great saphenous vein (GSV).', 'In all, 355 consecutive vein mappings were retrospectively analyzed. A generalized estimating equations approach to linear logistic regression was used to evaluate the variables.', 'Among the 312 vein ablation of the GSV, 10 (3.2%) developed EHIT. When comparing the group of patients who developed EHIT versus no EHIT, the mean GSV diameter was 13.05 ± 5.59 mm versus 8.39 ± 3.38 mm (odds ratio [OR]: 1.25, P = .001), the presence of valvular incompetence at the saphenofemoral junction (SFJ) was 10.71% versus 0.44% (OR: 27.75, P =.001), and 3.09% in RFA versus 3.33% in EVLT (OR: 1.09, P = .89).'] Does vein mapping prior to endovenous catheter ablation of the great saphenous vein predict risk of endovenous heat-induced thrombosis?