Sarcoids are a locally invasive cutaneous fibroblastic neoplasia and are the most common skin tumor of equids. Myriad treatments are described in the literature including surgery, topical blistering agents, cryosurgery, immunotherapy, and intralesional chemotherapy. Recurrence or progression of the disease after treatment is common. Two years ago the authors began clinical trials investigating the feasibility of photodynamic therapy for the treatment of sarcoid tumors. The tumor or surgical margins were treated using topical or intra-lesional delta-aminolevulinic acid (ALA) as a photosensitizing agent. The ALA was left in situ for a period of time allowing buildup of protoporphyrin IX (the photosensitizer) prior to irradiation with a 635-nm diode laser. We have initial results in 10 patients with 18 lesions and have seen decrease in tumor size or complete remission in 13 of 18 lesions. Recurrence or progression has been noted in 7 lesions. Results of these trials and follow-up information on clinical patients will be presented for review.