We sequenced the factor VII gene (F7) in two unrelated Japanese patients with factor VII (FVII) deficiency. In the first (an asymptomatic 46-year-old man with FVII activity and antigen levels of 1.2% and 21% of normal respectively), novel E25K and H348Q mutations were identified in the doubly heterozygous state. In transiently transfected HEK293 cells, the level of FVII-E25K mutant activity in the culture media was significantly lower than that of FVII wild type, whereas the antigen levels of both proteins were similar. This suggests that the E25K mutation is associated with a dysfunctional FVII molecule. In the second patient (a 47-year-old woman with FVII activity and antigen levels of less than 1% and 6% respectively), an IVS4+1 mutation and a novel -96C to T transition were detected in the double heterozygous state. In electrophoretic mobility shift assays, the -96T mutation was shown to disrupt binding of Sp1.