The results of a study of Inter-Alpha-Trypsin Inhibitor (ITI) polymorphism in 281 blood samples are reported in this paper. These samples were taken from healthy individuals of both sexes, unrelated and resident in the Province of Cadiz. The frequency of ITI*1 was 0.617 and of ITI*2 was 0.383. The probability of exclusion in paternity testing was 0.18.