X-linked recessive congenital motor nystagmus was identified in two Chinese families living in the Guangdong province of China. Nystagmus was noticed in early childhood. Only males in the families were affected and all obligate carriers did not have nystagmus. Linkage study was performed using microsatellite markers at about 10 cM intervals on the X chromosome. The nystagmus in these two families is linked to markers in the region of chromosome Xq23-q27, including DXS1001, DXS8009, and DXS1047. DXS1047 gave the highest lod score of 3.53 at theta = 0.