Patients between the ages of 8 and 75 years who are enrolled in NIH s study of von Hippel-Lindau disease may be eligible for this 5-year study. Participants will have magnetic resonance imaging (MRI) of the brain and spinal cord and a thorough neurological history and examination at the start of the study. A blood sample will be taken for analysis of factors (hormones or other proteins) that may predict tumor growth. Follow-up clinic visits every 6 months will include a physical and neurological examination, blood tests, and MRI scans of the brain and spine. If symptoms or tumor growth requires more frequent follow-up, scans will be done at 3-month intervals.