One third of human cancers have a hormonal basis. Breast cancer, the most common cancer of women, is increasing in many countries, as is prostate cancer, the second most common cancer of men. Concurrently, molecular biology has refined the definition of hormones to include the interaction between tumor cells and both locally and distantly secreted factors. This volume in the series Cancer: Clinical Science in Practice considers aspects of hormonal cancer, including the molecular basis for the autocrine and paracrine regulation of cancer, molecular strategies for cancer detection, strategies in limiting the epidemic of hormonally related cancers, and new treatment approaches.