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 methylene tetrahydrofolate reductase (MTHFR) interacted with cigarette-cannabis smoking, reducing vasodilatory nitric oxide (NO), promoting arterial spasm-thrombosis. Of 21 smoking BD patients (14 men [2 siblings], 7 women; 20 white, 1 African-American), compared to 21 age-gender-race matched healthy controls, 5A/6A stromelysin- 1 homozygosity was present in 7 of 21 (33%) BD cases versus 5 of 21 (24%) controls (risk ratio 1.4; 95% confidence interval [CI] 0.5-3.7), and eNOS T-786C homozygosity was present in 3 of 21 (14%) BD cases versus 1 of 21 (5%) controls (risk ratio 3.0; 95% CI 0.3-26.6). C677T MTHFR homozygosity or compound C677T-A1298C heterozygosity was present in 7 of 21 cases (33%) versus 11 of 21 controls (52%) (risk ratio 0.6; 95% CI 0.3-1.3). In 18 patients who stopped and 3 who continued smoking, all stromelysin-1 5A/6A and/or eNOS heterozygotes-homozygotes, superficial phlebitis, lower limb gangrenous ulcers, and intractable ischemic rest pain with arterial occlusion progressed despite conventional medical therapy, threatening amputation. In 15 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 (2000 mg/day) to optimize homocysteine metabolism and reduce asymmetric dimethylarginine, a NO synthase inhibitor. Unexpectedly quickly and strikingly, within 8 weeks to 8 months receiving l-arginine-folic acid, 11 of 15 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 and eNOS T-786C 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.