A clone expressing the 3' end of the RESA gene of the Palo Alto isolate of Plasmodium falciparum was isolated by screening a lambda expression library of Mung bean nuclease-digested genomic DNA fragments with antibodies from malaria patients. The DNA sequence of the RESA gene of this isolate has seven single-base changes compared to that seen in the Papua New Guinean isolate FC27. Six of the seven mutations cause amino acid substitutions. The same amino acid sequence as the Palo Alto sequence is found in the Ghanaian isolate NF7. To determine whether these are the only changes in this region of the molecule, we performed PCR analyses on 12 blood samples from malaria patients from Indonesia. The Palo Alto form of the RESA gene was detected in 10 of the samples and the FC27 form of the gene was detected in the other 2 samples. No other forms of the RESA gene were found, suggesting that RESA exists in two alleles for the examined region of the gene. These results indicate that there are two major allelic forms of RESA present in this part of Indonesia.