Acidic ethanol precipitation, gel-filtration chromatography (Sephadex G-25) and capillary isotachophoresis were performed on serum and tumor tissue samples from eight patients with stage III and IV laryngeal cancers. An anionic 0.3-5 kDA molecular mass substance that was probably peptide was recorded in both the serum and cancer tissue, but could not be shown in the serum of five control subjects. This substance disappeared from the sera of four patients after total laryngectomy and they have now lived without tumor recurrence for about 2 years. Three of the other four patients developed tumor recurrences while one patient has remained tumor-free. Our findings support a hypothesis that the peptide-like molecule is characteristic of laryngeal cancer and can possibly be used for monitoring the disease.