Screening refers to testing people without symptoms to detect diseases early when treatment is most effective. Common screening programs include mammograms for breast cancer, Pap tests for cervical cancer, colonoscopies for colon cancer, and blood pressure checks for cardiovascular disease. Effective screening identifies conditions before symptoms appear, improving treatment outcomes. Provincial health programs determine which screenings are covered and recommend screening schedules based on age and risk factors. Not all screening is beneficial—some conditions don't benefit from early detection, and screening can cause anxiety or unnecessary treatment. Public health authorities evaluate screening programs for net benefit before implementation.