Epidemiological studies reveal an inverse relationship between garlic consumption and death rate for gastric cancer in populations in China. These reports suggest a role for garlic in the prevention of human cancer. Garlic has been shown to inhibit the growth of transplantable tumors and to reduce the incidence of certain spontaneously-occurring tumors. Components of garlic have also been found to inhibit the activity of diverse chemical carcinogens during both the initiation and promotion phases of carcinogenesis. There is additional evidence that components of garlic modulate specific and nonspecific anti-tumor immunity. Recent literature suggests that a wide range of mechanisms are available to account for the biological activities of garlic.