The genetic polymorphism of red blood cell glyoxalase I (GLO) has been investigated in 9 population groups in Israel: Ashkenazi Jews, non-Ashkenazi Jews from Iran, Iraq, Balkan, North Africa, Yemen, Turkey and Egypt as well as Arabs living in Israel. The distribution of GLO1 and GLO2 genes in the 9 communities was not homogeneous (x2 = 14.48; d. f. = 8; p < 0.0005). Jews from Iran were found to have the lowest GLO1 frequency (0.2294), while those from Egypt had the highest gene frequency (0.3968). The other investigated communities were shown to have intermediate values for this gene frequency. No significant difference has been found between Ashkenazi and non-Ashkenazi Jews (with the exception of those from Egypt) or Arabs living in Israel.