Thirty-three patients with moderate to severe recurrent laryngeal papillomatosis underwent photodynamic therapy at our institution. All received 2.5 mg/kg of dihematoporphyrin ether intravenously either 48 or 72 hours prior to photoactivation with an argon pump dye laser system. Photosensitivity was the only side effect seen. Statistical analysis showed a significant decrease, by approximately 50%, in the average rate of laryngeal papilloma growth following treatment. The response was especially pronounced in patients with the worst disease. In addition, three patients have now remained free of disease for extended periods following photodynamic therapy. Latent infection with human papillomavirus continues to persist in clinically normal tissue following photodynamic therapy. The results and potential of this exciting new therapy for laryngeal papillomatosis are described.