PI and TF subtypes were studied in a sample of 137 individuals of the Chueta population. In addition to the PI*M alleles, PI*S, PI*Z, and PI*F were observed in the PI system. In the TF system no TF*B or TF*D alleles were found. PI results were compared with those of some Jewish and non-Jewish populations. The relatively high frequency of PI*S is indicative of a substantial Spanish influence. There are no previous data available on TF*C subtypes in Jews. The very low TF*C3 frequency in Chuetas (lower than in Spain) indicates that this allele may be extremely rare or absent in other Jewish populations.