Buerger's disease (BD) etiologies are poorly understood. Beyond smoking cessation, medical-surgical treatments have limited success. We hypothesized that mutations associated with arterial vasospasm (stromelysin-1 5A/6A, eNOS T-786C) and C677T-A1298C methylenetetrahydrofolate reductase (MTHFR) interacted with cigarette-cannabis smoking, reducing vasodilatory nitric oxide (NO), promoting arterial spasm-thrombosis. Of 19 smoking BD patients (13 men [2 siblings], ± women, 18 Caucasian, 1 African American), compared to 200 healthy Caucasian controls, BD patients were more likely to have 6A6A stromelysin-1 homozygosity (7/19 [37%] vs 46/200 [23%]) and to have eNOS T-786C homozygosity (3/19 [16%] vs 22/200 [11%]), but these patient-control differences were not significant, p = .4, 0.5. C677T MTHFR homozygosity or compound C677T-A1298C heterozygosity did not differ in patients vs controls (6/19 [32%] vs 70/200 [35%]), p = .8. In 9 patients who stopped and 1 who continued smoking, all stromelysin-1 5A/6A and/or eNOS heterozygotes-homozygotes, lower limb gangrenous ulcers, and intractable ischemic rest pain with arterial occlusion progressed despite conventional medical therapy, threatening amputation. In these 10 patients, to increase vasodilatory NO via endothelial NO synthase, L-arginine (15 g/day) was given, along with folic acid 5 mg, vitamin B6 (100 mg), and B12 (2,000 μg/day) to optimize homocysteine metabolism and reduce asymmetric dimethylarginine, a NO synthase inhibitor. Unexpectedly quickly and strikingly, within 8 weeks to 8 months on L-arginine-folic acid, all 10 treated patients improved with uniform pain reduction, ulcer healing, and in 5, full recovery of previously absent peripheral pulses. In smokers homo-heterozygous for stromelysin-1 5A/6A, eNOS T-786C, and C677T-A1298C MTHFR mutations, we speculate that the development and severity of BD are related to a gene-environment vasospastic interaction with reduced NO-mediated vasodilatation. Increasing NO production by L-arginine while optimizing homocysteine metabolism by folic acid-B6-B12 may have therapeutic benefit. Further blinded, placebo-controlled studies are needed to determine whether our observations can be generalized to larger BD cohorts.