Garlic (Allium sativum) has had an important dietary and medicinal role for centuries. It is now known that garlic contains chemical constituents with antibiotic, lipid-lowering, detoxification, and other medicinal effects in the body. This article reviews some of the physiological characteristics of garlic and examines the relationship between garlic and cancer prevention and treatment. Hypotheses regarding the possible role of garlic in modulating mechanisms that may alter the carcinogenic process are discussed.