Screening is defined as identification of individuals within an asymptomatic population who have specified disease at a time when intervention may result in improvement of prognosis of the disease. Identification of the disease at the earlier phases of progression improves prognosis. All kinds of cancer screening may not have same benefit. Screening for breast cancer has been found to be beneficial. Randomized controlled trials and meta-analysis have shown that screening by mammography reduces breast cancer by 25% and can significantly reduce mortality from breast cancer. This article reviews methodology and bias, modalities, benefits, problems, results and current guidelines of breast cancer screening.