To improve the survival in breast cancer, it is important to detect and treat breast cancer early. Physical examination (PE), mammography (MMG), ultrasonography (US), and aspiration biopsy cytology (ABC) are routinely assessed in the diagnosis of breast cancer. When three procedures including ABC are positive in a diagnosis of breast cancer, it is an absolute indication for surgery. Of all 238 breast cancers between 1987 and 1992, 86 cases were T1. The sensitivity of each procedure was PE 58.9%, MMG 70.0%, US 74.4% and ABC 86.2%, indicating that PE was less sensitive for small cancer. The recent accuracy of ABC in our series was satisfactory, and the combination diagnosis had a good result for T1 tumor because the findings from these procedures were complimentary. The high accuracy of ABC therefore suggests that lumpectomy has two aspects, definite diagnosis, and therapy as conservative surgery for breast cancer. The nineteen cases of T0 cancer encountered were almost entirely detected by nipple discharge or MMG. In conclusion, the combination diagnosis including ABC was very effective, and it is very important to detect and diagnose clinically small or non-palpable breast cancer.