The single-strand conformational polymorphism technique was used to search for neutral polymorphisms in 18 PCR-amplified dystrophin gene fragments. Out of the seven polymorphisms (six intronic and one exonic) detected in Caucasians, one was absent from the Oriental population. Significant differences in allele frequencies between the two populations were observed for three of the intronic polymorphisms. In Caucasians, one variant position occurred per 728 bp of the total DNA or one per 483 bp of the intronic sequence; the corresponding average heterozygosities were 0.04 and 0.06%, respectively.