Li-Fraumeni syndrome (LFS) is a cancer predisposition syndrome associated with high risks for a broad spectrum of cancers including early-onset cancers. Five cancer types account for the majority of LFS tumors: adrenocortical carcinomas, breast cancer, central nervous system tumors, osteosarcomas, and soft-tissue sarcomas. Other cancers associated with LFS include leukemia, colorectal cancer, stomach cancer, lung cancer, melanoma, pediatric head and neck cancers, pancreatic cancer, and prostate cancer. Cancer survivors are at increased risk for developing additional primary cancers and treatment-related secondary cancers. The lifetime risks of cancer for women and men with classic LFS are 90% and 70%, respectively, and 50% of cancers occur prior to age 40 years.