We report 72 non-diabetic patients with obliterant atherosclerosis, stadium II, (intermittent claudication). The medium age of these patients was 62 +/- 4.5 years old. They were randomly included into four groups. Three were treated with Ozone: one of them by endovenous way, other intramuscular way, and the last one by rectal way; meanwhile, in the fourth group the patients were submitted to conventional medical treatment (control group). In the three ozone-groups there weren't differences when they were compared between then. But there was a significant improvement in comparison with the control group. The claudication distance in the treadmill increased to the 2.5 km/hour. Ankle/arm pressure rates hadn't significant differences, this corroborates the ozone action on the microcirculation. The least uncomfortable, the more harmless and the more economic way was the rectal way.