Cancer prevention is defined as the reduction of cancer mortality via reduction in the incidence of cancer. Examples of prevention strategies are avoiding a carcinogen or altering its metabolism; pursuing lifestyle or dietary practices that modify cancer-causing factors or genetic predispositions; and successfully treating preneoplastic lesions. Screening is detecting disease at earlier stage to improve outcome of cancer patient.Cancer incidence globally is increasing and reaches its maximum in developed countries in view of aging of the population, urbanization and adoption of industrialized life style. Risk factors of cancer are many and include physical, chemical, and environmental factors; however the most important of which and also preventable is cigarette smoking as smoking related cancer deaths annually are 148,000 cases in U.S.A. what gives rise to the importance of cigarette smoking prevention efforts.Certain cancers transmit through certain families and show genetic predisposition, this allows for prevention and early detection of cancers in high risk people with genetic background of cancer. Modifying dietary habits and life style may reduce the incidence of cancer.The use of chemopreventive agents showed promising results by some of them like Tamoxifen in breast cancer prevention and NSAIDs in colorectal cancer prevention.