In the current study of the prognosis of all patients (N equals 70) with squamous cell carcinomas (SCC) of floor of mouth in Norway during the period 1963 to 1972, the authors found that patients with Rhesus (Rh) (D)-negative blood group had significantly poorer prognosis (mean 5-year survival, 8%) than patients with Rh (D)-positive blood group (5-year survival, 30%) (P equals 0.04). This extends the authors' previous observations in another group of oral cancer patients. The authors do not know the explanation for this association. However, the Rh gene locus is located on the short arm of chromosome 1 which reportedly has shown rearrangements in some head and neck SCC and other human neoplasms. The authors therefore speculate that the Rh gene locus may be linked with chromosome 1 changes of importance for the progression of oral SCC.