Cellular retinol-binding protein (CRBP) concentration was determined by radioimmunoassay in biopsies from normal mucosa and squamous-cell cancers of the head and neck region in 26 patients. The plasma concentrations of retinol, retinol-binding protein (RBP), prealbumin, albumin, orosomucoid and alfa1-antitrypsin were also determined. In all patients the tumours contained significantly higher concentrations of CRBP (median = 185 micrograms/g tissue protein; range: 27-1,017 micrograms/g) than normal mucosa (median = 14 micrograms/g tissue protein; range 6-97 micrograms/g). CRBP could not be detected in patient plasma. The tumor/normal mucosa CRBP concentration ratio showed a significant inverse correlation to a histopathological malignancy grade score evaluating the tumour-host relationship, suggesting that tumours with high CRBP relative to normal mucosa are biologically less aggressive. Tumour CRBP showed no correlation either to CRBP concentration in normal mucosa, or to plasma retinol or plasma retinol-binding protein concentration. CRBP concentration in normal mucosa, however, showed a significant correlation to plasma retinol-binding protein concentration. Most of the patients had low levels of plasma retinol and retinol-binding protein compared to matched controls. Whether this has any relationship to the development of the tumour, or whether the active inflammation induced by the cancer leads to a low plasma retinol concentration, is unknown.