Juvenile retinoschisis is a rare, X linked hereditary vitroretinal degeneration. Female carriers of the disease do not develop any ocular abnormalities. Therefore, carrier detection by DNA analysis is extremely useful for these females. In order to evaluate the usefulness of a new class of DNA markers for carrier detection in X linked juvenile retinoschisis, DNA carrier detection or carrier exclusion was carried out in four possible carriers for X linked juvenile retinoschisis. The use of these highly polymorphic CA repeats, closely linked to the RS gene, greatly enhances both the reliability and feasibility of carrier detection in X linked juvenile retinoschisis.