Mastitis is an inflammatory disease of the breast, which occasionally results from infectious microorganisms. Puerperal mastitis is the most common type of mastitis. Milk stasis is the main reason, and Staphylococcus aureus is the pri- mary causative organism. There is usually a history of difficulty in the breast- feeding. Unless symptomatic treatment is sufficient to recovery, antibiotherapy should be administered. Central or subareolar breast infection predominantly occurs in women in their third decade. The disease may present with recurrent signs of breast infection or abscess. There is history of smoking in 90% of pa- tient’s backgrounds. Nonlactational peripheral infection of the breast is rare, and may be idiopathic or associated with systemic diseases such as diabetes mellitus and rheumatoid arthritis. Idiopathic granulomatous mastitis (IGM) is the most frequent granulomatous disease of the breast, which generally repre- sents as rapidly grown painful breast mass. The diagnosis of IGM is mistaken for breast carcinoma in half of the cases. The disease is frequently associated with recent pregnancy and lactation. Diagnosis of IGM is established by trucut biopsy. Surgical excision or immunosupressive therapy with corticosteroids can be ap- plied in the treatment. All breast infections may proceed to breast abscess. In the earlier period of an abscess, treatment is provided by ultrasonograhy guided aspiration but in the late period via an incision and drainage.