X-chromosomal DNA probes defining various polymorphic DNA markers were used to study genetic linkage in three families with Alport's syndrome. With the DXS17 marker, only a single cross-over was observed in 26 informative meioses, and evidence for linkage was also obtained with the DXS11 marker. These data localize the gene for the X-linked form of Alport's syndrome to the middle of the long arm of the X chromosome.