A group of 30 patients ranging from 4 to 56 years of age with the peripheral form of neurofibromatosis were evaluated for the presence of iris (Lisch) nodules. These nodules were observed in 73% of our cases and their presence was directly related to the severity of the skin manifestations of the disease. It is concluded that Lisch nodules are pathognomonic for neurofibromatosis and thus, their presence should be looked for in all suspected cases.