Sclerosing therapy has in recent studies showed promising results in patients with clinically and ultrasonographically diagnosed tendinosis in Achilles and patellar tendons. The aim of this investigation was to study the presence of intratendinous colour Doppler (CD) flow in horses with clinically diagnosed chronic tendinopathy and to test if experience from human studies could be extrapolated to horses. Special interest was focused on the treatment with sclerosing therapy and whether we could obtain the same successful peroperative findings as in humans. Four horses with clinically diagnosed unilateral chronic tendinosis in the forelimbs were examinated with both grey-scale ultrasonography (US) and CD. The horses were to be euthanised according to standard procedure is such cases. The US findings were used for guidance of sclerosing therapy. All horses showed abnormal findings on US, especially intratendinous neovascularisation in the affected limb but not in the contralateral limb. The CD findings had the same appearance as seen in human Achilles tendons with chronic tendinopathy. In all cases the intratendinous neovascularisation was successfully "shut down" peroperatively. The horses showed no signs of discomfort or worsening of symptoms during the short follow-up period after the procedure. The results indicate that the promising results from human medicine might be transferred to treatment of horses with chronic tendinopathy. In the future it will hopefully be possible to use the model from overused tendons in the horse to determine the best treatment of overuse injuries in humans as well. The animal model will allow experimental studies including substantial tissue sampling for mechanical and molecular biological analysis.