In this study we have determined the frequency of beta(s) haplotypes in a Brazilian sickle cell disease population from Sao Paulo, Brazil, by analyzing sequence variations in the immediate 5' flanking and second intervening sequence (IVSII) regions of the gamma globin genes. This association between sequence differences and beta(s) haplotype backgrounds was determined by screening genomic DNA samples using dot blot analysis of polymerase chain reaction products. We studied 148 beta(s) chromosomes, and found that haplotype 20 (CAR or Bantu) signif icantly predominated in this population. This is in agreement with the findings of the historical Portuguese Atlantic slave446322327