The main advantage of photodynamic therapy (PDT) in laryngology seems to be its non-invasiveness and the possibility of using it despite previous application of conventional methods. In the study, we gave PDT to two separate groups of patients, i.e. five patients with advanced tumour (four of them with local recurrence (squamous cell carcinoma) after surgery and radiotherapy and one with a primary hypopharyngeal tumour) and five patients with leucoplakia. In the first group delta-aminolaevulinic acid (ALA) was administered orally (dose 3 g), while in the second, an ointment containing 10% ALA was applied locally. In both groups prior to irradiation, the tissue level of protoporphyrin IX was verified using an adapted Xillix Life instrument. All treated lesions were irradiated with an argon-pumped dye laser (dose range 100-250 J/cm2, wavelength 635 nm). In the first group, partial response was obtained. In these advanced cases, diminution of cancerous ulcerations was observed. In the leucoplakia group, complete response was achieved in four out of five treated patients. On the basis of our preliminary results, PDT may be useful in eradicating premalignant lesions of the oral cavity and in the palliation of advanced lesions of the oropharynx and larynx.