The OPR was studied in 203 patients with squamous cell carcinoma of the head and neck at the time of diagnosis, before any specific treatment. The mean initial OPR value was significantly higher in cancer patients than in 63 healthy controls: 5.29 +/- 3.09 vs. 2.63 +/- 1.07; P less than 0.001. There was no significant difference by anatomic site, but the OPR was significantly lower in stage I-II disease than in stage III-IV: 5.10 +/- 3.85 vs. 3.23 +/- 1.99, P less than 0.001. An initial OPR under or over 6 seems to be an important prognostic factor: at 2 years, 51% of patients with an OPR less than 6 were alive vs. only 24.5% of those with an OPR greater than 6, P less than 0.001. The difference was also noted in patients with stage III-IV disease (mean survival: 16 months vs. 7 months, P less than 0.001) and in 89 of the patients who received chemotherapy (mean survival 16 months vs. 6 months, P less than 0.001) whatever the response to chemotherapy. The OPR index, which explores nutritional and acute phase reactant proteins, seems to reflect the host-tumor relationship. Its initial value is strongly related to prognosis at 2 years.