To date, five α-1,3-fucosyltransferase genes (Fuc-TIII, IV, V, VI, and VII) have been cloned. To examine the role of α-1,3-fucosyltransferase in the synthesis of sialyl Lewis x and the prognosis of lung cancer, PCR amplification of five fucoyltransferase genes and immunohistochemical staining of sialyl Lewis x were performed in 333 patients with lung cancer who underwent surgical resection from 1980 to 1993. The frequencies of Fuc-TIII/V, Fuc-TVI, Fuc-TIV, and Fuc-TVII expression were 9%, 26%, 75%, and 66%, respectively. The frequency of sialyl Lewis x expression (75%) was comparable to Fuc-TIV and Fuc-TVII expression. However, the grading of sialyl Lewis x staining correlated only with the grading of Fuc-TVII gene amplification. Survival of the patients whose tumors showed strong expression of Fuc-TIV and/or FucT-VII was significantly shorter than that of the patients whose tumors did not express either Fuc-TIV or Fuc-TVII. These results suggest that Fuc-TIV and Fuc-TVII expression may be of prognostic value among patients with lung cancer by participating in the biosynthesis of sialyl Lewis x.