The authors studied retrospectively clinical data of seventy cases with breast cancer during pregnancy and lactation.They were treated and diagnosed by operation and pathology.Primary factors influencing prognosis were analyzed.It was demonstrated that 5year survival rate of the patients were significantly influenced by clinical stage , month of pregnancy and lactation, time of symptoms, type of operation, type of pathology, histological grade of malignancy, recurrence and metastasis, and estrogen receptor status (Ｐ＜0.05).Age and termination of pregnancy had no beneficial effect on survival (Ｐ＞0.05).The prognosis of pregnant and lactating breast cancer was poorer than ordinary breast cancer.Their 5year survival rate were 55.7% and 74.3%, respectively. After they were matched for stage and for age, no difference in survival was found.Early diagnosis and radical operation combined with radiotherapy, chemotherapy and hormonal therapy have better prognosis.The method can shorten time of treatment and improve survival rate.Termination of pregnancy has not been shown to improve survival and shall not be advised routinely.Future pregnancy may be detrimental and shall be discouraged.