Objective: To present the theory, technique, and results of photodynamic therapy for the treatment of oral, laryngeal, and head and neck cancers. Study Design: Retrospective review of the literature of more than 500 patients with head and neck cancer treated with photodynamic therapy, as well as a retrospective review of the author's 107 patients treated with photodynamic therapy for head and neck neoplasia between 1990 and 1997. Methods: The literature was retrospectively reviewed, as were patient records, and tabulated for age, sex, site, and staging of lesions, with special focus on post-photodynamic therapy treatment outcome, long-term disease-free survival, and complications. Results: Twenty-five patients with carcinoma in situ and T1 squamous cell carcinoma of the true vocal cord who underwent photodynamic therapy treatment for cure obtained a complete response after a single photodynamic therapy treatment. Only one patient has had recurrence to date, with a cure rate to 79-month follow-up of 95%. Twenty-nine patients with carcinoma in situ and T1 recurrent squamous cell carcinomas of the oral cavity and tongue were treated. All obtained a complete response after a single photodynamic therapy treatment; however, five patients developed local recurrence with follow-up to 70 months, for an 80% cure rate. A review of 217 patients with early squamous cell carcinomas of the head and neck treated with photodynamic therapy in the literature demonstrated an 89.5% complete response rate. The most common complication in these patients was limited prolonged skin photosensitivity without any permanent sequelae. Conclusions: Photodynamic therapy is effective for treating carcinoma in situ and T1 squamous cell carcinoma of the larynx and oral cavity and may be of benefit as an adjuvant intraoperative treatment of stages III and IV tumors of the head and neck in conjunction with surgery and radiation therapy to improve cure rates. Further controlled studies need to be performed to further demonstrate the effectiveness of photodynamic therapy and the treatment of head and neck cancers.