Routine assessing of HER2 status is necessary for successful treatment of carcinoma of breast by Herceptin. Our results prove comparability of well standardized semiquantitative method by Hercep Test DAKO: both negative findings (73.4% in laboratory A, and 77.4% in laboratory B) and positive findings (26.6% in laboratory A, and 22.6% in laboratory B) corresponded both with each other and with the DAKO's reference data. The study also testifies to problems with interpretation of the IHC data (primary antibody c-erbB-2-oncoprotein DAKO). The problems concern particularly the processing standards, the dilution of antibodies, the application of IHC automatic machine, and probably also the detection system. It is suggested that each laboratory develops a standardized IHC protocol, in coordination with other laboratories. Thus, standardization of both processing and evaluation of the results will be achieved. As the indication for treatment by Herceptin is connected with HER2 overexpression, it is suggested to follow the algorhythm of HER2 examination presented by Nenutil at the ROCHE Satellite symposium.