Studies on migrants can generate important clues on the etiology of cancer. The purpose of the present study was to determine the relationship between ethnic origin and the incidence of oral and pharyngeal cancers among residents of the Thames regions in southern England. Records from the Thames Cancer Registry during the period 1986-91 were examined and south Asians and Chinese ethnic immigrants flagged using their place of birth and names. Computation of relative incidence among head and neck cancers (n = 7222) showed that oral cancer was significantly higher among Asians (95/232 = 40.9%) and nasopharyngeal cancer among Chinese (45/67 = 67.2%). Some differences in the intra-oral site of cancer and ethnic origin were noted. The ethnic migrants were significantly younger (Asians 51.6 +/- 34.8 years, Chinese 47.6 +/- 14.8 years) compared to the rest of the population (64.8 +/- 15.6 years) at the time of cancer diagnosis (p = 0.0) but no significant differences were found for the stage of presentation. The mean survival period for a cancer of the head and neck was 2.2 years and significant differences in cumulative rates of survival were noted among the three groups studied (p = 0.003). A strong correlation was noted between the incidence of oral cancer and local authorities with a high percentage of Asian residents. The south Asian and Chinese ethnic minorities constitute important high risk groups for oral and nasopharyngeal cancer, for whom targeted prevention is indicated.