G6PD deficiency mutational profile and haplotype diversity using 6 RFLPs (FokI/PvuII/BspHI/PstI/BclI/NlaIII) and a (CTT)(n) microsatellite, were investigated in 70 G6PD-deficient Portuguese individuals. All but one G6PD A-(376G/202A) variants (44/45) have a single haplotype (+/+/-/+/-/+/195). G6PD Betica(376G/968C) alleles (n=10) have a single RFLP haplotype (+/-/-/+/-/+) and 4 different (CTT)(n) repeats. Age estimates based on microsatellite variation suggest that Betica mutation arose 900 generations ago. G6PD SantaMaria(376G/542T) allele was found on haplotype (+/-/-/+/-/+/201) and 10 G6PD variants on RFLP haplotypes (-/-/+/+/-/-), (-/-/+/+/-/+) and (-/-/+/+/+/+).