Haemophilia A (HA) is an X-linked bleeding disorder caused by mutations in the factor VIII (FVIII) gene. Identification of these mutations is becoming increasingly important in a variety of clinical settings. The purpose of this report is to describe our experience of FVIII gene mutation analysis in the largest cohort of patients in Taiwan including the discovery of 21 novel mutations. We tested 115 HA patients from 91 unrelated families, including 79 severe, 15 moderate and 21 mild types starting with an assay for the intron 22 inversion by long range-PCR followed if necessary by additional genetic studies. Intron 22 inversion accounted for 27.8% of the total and 36.7% of severe HA patients respectively while intron 1 inversion comprised 7.6% of severe patients. These were clearly different from the known data in caucasian populations. Of 75 patients without intron 22 or 1 inversion, 70 from 62 unrelated families revealed 56 different mutations by denaturing high-performance liquid chromatography (DHPLC), of which 21 were novel. Also, the only female patient with severe HA was found to have heterozygous non-sense mutation (c.6683G>A) of exon 24. Seven patients, including five without amplified PCR product and two without encoded DNA defect turned out to have exon(s) deletion or insertion by reverse transcript PCR (RT-PCR). In our study, the combination of various molecular techniques including LR-PCR, multiplex PCR, DHPLC and RT-PCR analysis enabled definitive detection of the causative FVIII gene defects in 112 of 113 (99%) HA patients.