41 families with classic Alport's syndrome (hereditary nephritis with sensorineural deafness) were studied. All their pedigrees were compatible with X-linked inheritance. DNA probes were used to investigate genetic linkage in these families. Linkage to probe S21 (DXS17) was confirmed (LOD score = 4.72 at 0 = 0.06), localising the gene for Alport's syndrome to the middle of Xq; thus the disorder is X-chromosomal in nature.