As it is well established that an association exists between congenital bilateral absence of the vas deferens (CBAVD) and cystic fibrosis gene mutations, we investigated CFTR(TG)m(T)n polymorphism within a Taiwanese population that exhibits a very low incidence of CF. Sixty-three patients with CBAVD and 86 age-matched normal control subjects were evaluated. Temporal temperature gradient gel electrophoresis was used for CFTR mutational analysis. No major CFTR mutation was found in the patient series. A single prominent CFTR mutation, IVS8-5T, was present; however, (50.8% of 63 cases and 33.3% of 126 alleles), and exhibited a high prevalence of 12 or 13 TG repeats (93.8% of 32 cases and 95.2% of 42 alleles with IVS8-5T). Although these results are similar to those of Japanese CBAVD patients, they are higher than the common frequency (about 21%) found among Caucasian CBAVD patients. The very high percentage (42.9%) of patients with no CFTR mutations is also an ethnic characteristic. We concluded that CBAVD patients from Taiwan, who express a very low incidence of CF, were less affected by CFTR mutations, with the exception of IVS8-5T linked to either 12 or 13 TG repeats, which does exhibit a high prevalence among CBAVD patients tested.