Coagulation factor XIIIA and XIIIB polymorphisms in a random population sample from Chengdu in southwest China (n = 121) were studied using isoelectric focusing in polyacrylamide gels followed by immunoblotting with enzyme immunoassay. The allele frequencies were as follows: FXIIIA*1 = 0.8719, FXIIIA*2 = 0.1240, FXIIIA*3 = 0.0041; FXIIIB*1 = 0.2727, FXIIIB*2 = 0.0165, FXIIIB*3 = 0.7107. The distribution of phenotypes of FXIII agrees with the Hardy-Weinberg equilibrium. Comparing these allele frequencies with those reported in other populations, it was found that the allele frequencies of FXIIIA*1 and FXIIIB*3 in the Chinese population were higher.