Cancers are a large family of diseases which involve abnormal cell growth with the potential to invade or spread to other parts of the body. They form a subset of neoplasms. The aim of the work to show the magnitude of the problem of cancer, The possible etiologic causes of cancer in general as the great majority of cancers, are due to environmental factors. The remaining are due to inherited genetics. Common environmental factors that contribute to cancer death include tobacco (25–30%), diet and obesity (30–35%), infections (15–20%), radiation (both ionizing and non-ionizing, up to 10%), stress, lack of physical activity, and environmental pollutants. How to early detect cancer and Screening of the general population. Preventive measures applied certain types of cancer such as diet,medications,vitamins and vaccines.