To define genetic and sexual determinants in the genesis of rhabdomyosarcoma, we compared gene expression of primary tumors and of preneoplastic urethral tissue of BALB-p53Neu mice with urethral tissues of various congenic mice not prone to rhabdomyosarcoma onset, including female BALB-p53Neu mice, “wild-type” BALB/c mice (indicated as p53+/+ for clarity) and mice carrying either inactivated p53 alleles (both p53+/− and p53TM/TM), or an activated HER-2/neu transgene. This evidence concerns the gene ERBB2 and rhabdomyosarcoma.