Neurofibromatosis type 1 (NF1) is the most common neurogenetic disorder, affecting similar to 1 in 3,500 individuals worldwide. Mutations of the NF1 tumor suppressor gene predispose individuals to a variety of benign and malignant tumors. Rhabdomyosarcoma (RMS) is an uncommon malignant soft tissue sarcoma and is also a rare tumor type in NF1 patients. We report two cases of NF1 with RMS. The first is that of an infant with overlapping phenotypic features of NF1 and Noonan syndrome (NS) who presented with RMS of the bladder. The second infant likewise exhibited NF1 features and was also associated with bladder RMS. DNA samples were extracted from peripheral blood and tumor tissue samples. We performed loss of heterozygosity (LOH) analysis of the NF1 gene by using seven intragenic markers (IVS27AAAT2.1, IVS27EVI-20, IVS27AC24.8, IVS27AC28.4, M98509, IVS27AC33.1, IVS38TG53.0) and one extragenic polymorphic marker (3' NF1). A large deletion was detected in the NF1 gene in the NF1-Noonan syndrome (NF-NS) case associated with RMS. (c) 2006 Elsevier Inc. All rights reserved.