Breast cancer is the most frequent malignant disease in women. It is alarming that in most countries and including Slovenia the number of women afflicted by and dying of this disease is increasing every year. The causes for the occurrence of the disease are unknown. In some women the risk of developing breast cancer is higher than in others. Breast cancer can be detected in the noninvasive and invasive form. Various investigation methods are used in breast cancer detection: history, clinical investigation, mammography, ultrasound, needle and excision biopsy. The probability of survival is greater if the disease is discovered at an early stage. Screening of asymptomatic women by clinical investigation and mammography is an effective method for the detection of early cancer forms. Together with adequate treatment it will certainly decrease the mortality due to this disease.