We have examined the expression of two newly identified members of the EGF family, cripto and amphiregulin (AR), in a series of 58 primary rectal carcinomas and adjacent non-involved mucosa by immunohistochemical staining using rabbit polyclonal antibodies. More than 90% (53/58) of rectal carcinomas showed AR immunoreactivity whereas cripto was found in 41 out of 58 (71%) tumours. Cripto immunoreactivity was most frequently seen in tumours arising in the lower third of the rectum (p<0.01) and in flat and excavated lesions (p<0.05). Out of 54 normal rectal mucosae adjacent to carcinoma 20 (37%) showed cripto immunoreactivity and all showed a trend towards a higher recurrence rate. Ten of these 20 (50%) rectal tumours showed less cripto immuno-reactivity than the adjacent normal mucosa and were penetrating through the bowel wall and recurred within 5 years. There was a correlation between increased cripto immunoreactivity in the normal mucosa and lymph node involvement (p=0.01). AR immunoreactivity was present in the majority (52/58, 94%) of the normal mucosae adjacent to tumours. No correlation was found between AR immunostaining, histology and prognosis.