We compared trastuzumab alone therapy (A-group) (n=6) to trastuzumab plus taxane therapy (B-group) (n=12) in patients of advanced and metastatic breast cancers. The response rate of A-group was 33.3%. Six months after, A-group was switched to trastuzumab plus taxane therapy. The response rate of A-group after addition of taxane was improved to 83.3%. The mean duration of response was 6.8 months in A-group after addition of taxane. The response rate of B-group was 83.3%. The mean duration of response was 7.5 months in B-group. The combination therapy of trastuzumab and taxane therapy showed a high response rate. We think that it is possible to start trastuzumab alone therapy because A-group after addition of taxane showed a high response rate. There were no significant differences of immunosuppressive acidic protein (IAP) from the course of chemotherapy in all cases.