Cancer chemo prevention refers to the use of agents for the inhibition, delay, or reversal of carcinogens before invasion. In the present review, agents examined in the context of cancer chemo prevention are classified in four major categories—hormonal, medications, diet-related agents, and vaccines—and the main representatives of each category are presented. Although there are serious constraints in the documentation of effectiveness of chemo preventive agents, mainly stemming from the long latency of the condition they are Addressing and the frequent lack of intermediate biomarkers, there is little disagreement about the role of aspirin, whereas a diet rich in vegetables and fruits appears to convey more protection than individual micro nutrients. Among categories of cancer chemo preventive agents, hormonal ones and vaccines might hold more promise for the future. Also, the identification of individuals who would benefit most from chemo preventive interventions on the basis of their genetic profiles could open new prospects for cancer chemo prevention.