The expression of cytoplasmic c-erb B2, epidermal growth factor receptor (EGFR), proliferating cell nuclear antigen (PCNA) and dipeptidylpeptidase IV (DPP IV) was significantly higher in sporadic cancer of the right than of the left colon. In addition, cytoplasmic c-erb B2 displayed the same difference in the adjacent (less than 2 cm) and distant (more than 5 cm from the tumour margin) mucosa. The findings cannot be related to Dukes staging. It is suggested that different ontogenic development of the right (from the midgut) and the left (from the hindgut) colon may be a possible explanation. Therefore, data on the expression of different molecular markers in colorectal cancer and surrounding mucosa should always be supplemented by data on tumour location.