Congenital and acquired nystagmus, particularly pendular and jerk nystagmus, see-saw nystagmus and spasmus nutans, may be the presenting sign of a suprasellar mass lesion.(1) The large variety of different suprasellar mass lesions requiring quite different therapeutic measures necessitates exact histological diagnosis for optimal therapeutic strategy planning.(2) Stereotactic tumor biopsy has become a well-established diagnostic approach, combining minimal surgical trauma with a high degree of diagnostic safety. Particularly in the two most frequent suprasellar mass lesions - craniopharyngiomas and pilocytic astrocytomas - accurately planned stereotactic drainage of tumor cysts combined with radiotherapy and/or stereotactic radiosurgery allows successful decompression and tumor control as well as maximum preservation of visual and endocrinological functions when compared with conventional surgical procedures.(2-11)