The level of expression of six breast cancer-associated antigens or markers (CEA, NCRC-11, HMFG1, HMFG2, D8 and DF3) in primary tumour tissue and patients' serum has been compared. Two-hundred-and-forty-five consecutive patients with newly-diagnosed breast cancer had tumour biopsy and serum samples taken prior to any anti-cancer therapy (Stage I and II disease n = 100, Stage III disease n = 60, Stage IV disease n = 85). No correlations were found between the level of tumour tissue staining and serum levels of the same antigens. Those samples from patients with Stage IV disease were also analysed separately but again no correlations were observed. Therefore the staining pattern of the primary tumour for these antigens is not a predictor of which tumour marker will be elevated in the serum.