Two multi-allelic microsatellite polymorphisms within the factor VIII gene were studied in 138 Chinese subjects. The allele sizes detected were higher than those found in Caucasian populations, whereas the heterozygosity rates were lower, being 0.5370 for intron 13 and 0.4444 for intron 22 repeats respectively. Their usefulness in diagnosis was compared to other intragenic and extragenic RFLPs, using previous data on the same 31 unrelated haemophilia A families. These intragenic microsatellite repeat polymorphisms were only informative for 18/31 families (58%); however, with the combined use of all existing RFLPs, the cumulative informativeness would be 100%.