[Undescended testis: current views and advice for treatment].

--Undescended testis (UDT) is one of the most common urogenital abnormalities in boys. --UDT is defined as a testis which cannot be brought into a stable scrotal position. --At present, congenital and acquired forms of UDT are recognised. Congenital UDT is defined as a UDT which has never descended from birth. Acquired UDT is defined as a UDT which has been fully descended in the past. --Congenital UDT should be treated surgically between 6 to 12 months of age. --The treatment of acquired UDT is still disputed. As yet, awaiting spontaneous descent at early puberty seems to be the most rational treatment. --In the Netherlands, the high number of late orchidopexies is due to surgery for acquired UDT. To reduce this high number, the guidelines of the first development conference on 'non-scrotal testis' dating back to 1986 should be revised on several points.