Background: Neurofibromatosis 1 (NF1) is a relatively common autosomal dominant condition. Among the complications of the disease, such as neurological disorders, hypertension and skeletal deformities, malignancy is the most serious one and is the main cause of early death in these patients. Objective: Review of cases of NF-1 associated with malignancies. Patents and Methods: In a retrospective, descriptive study, 17 patients with malignancy and NF1 disease referred to oncology department of Qaem and Omid Hospitals (Mashhad) in a 10-year-period between 1993 and 2003 were reviewed. Results: 11 patients were male and 6 were female. The median age of patients was 23 years. We observed 9 cases with malignant peripheral nerve sheath tumors, 4 with CNS malignancies, 2 with rhabdomyosarcoma and one case with breast carcinoma. Conclusion: Regarding the importance of early diagnosis of these malignancies, and especially considering the young age of involved patients, it is logical to plot a schedule to examine the NF1 patients periodically. Physicians who are in contact with these patients should educate them to be aware of any suspicious signs and symptoms of malignancy.