This paper reports a randomised clinical trial of 81 patients with phlebostatic ulcers of the lower limbs who underwent treatment with topical application of Ozoile. The results were compared with a control group which did not receive the treatment. The trial lasted 9 months overall. Over this period of time, patients treated with Ozoile showed a statistically meaningful reduction (P>0.007) of mean re-epithelialisation time compared to the control group. Biopsies of the floor and margins of the ulcers treated topically with Ozoile were performed and analysed histologically and demonstrated that topical ozone application stimulates fibroblast proliferation and neoangiogenesis. Such mechanisms, combined with debridement and compression therapy, make for an efficient treatment strategy for phlebostatic ulcers, providing treated patients with a reduction of healing time and better quality of life.