One hundred thirty patients with neoplastic diseases of the larynx, oral cavity, pharynx and skin have been treated with photodynamic therapy (PDT) with follow-up to 79 months. Those patients with primary or recurrent leukoplakia, carcinoma-in- situ (CIS) and T1 carcinomas obtained a complete response after one PDT treatment and 87% remain free of disease. Sixteen patients with deeply invasive T2 and T3 carcinomas were treated with PDT. Of those sixteen, ten obtained a complete response, but six have recurred locally. Although a response can be achieved with PDT in the larger solid tumors, it is not a consistent complete response because of the depth of invasion of the tumor. This is due to the inability to adequately deliver laser light to the depths of the tumor bed. Fourteen patients with massive recurrences of squamous cell carcinomas were treated with intraoperative adjuvant PDT following tumor resection. Two patients developed a local recurrence within the field of treatment. PDT is highly effective for the curative treatment of early carcinomas (CIS, T1) of the head and neck. T2 and T3 superficial carcinomas, with invasion less than 0.5 cm, are also curatively treated with PDT with significantly reduced morbidity compared to conventional modes of treatment. Also, intraoperative adjuvant PDT may increase cure rates of large infiltrating carcinomas of the head and neck.