In Apc(Min/+) (Min; multiple intestinal neoplasia) mice two separate populations of aberrant crypt foci (ACF) develop in the colon after azoxymethane (AOM) exposure. ACF(Min), with a flat appearance, severe dysplasia and increased beta-catenin expression, are related to adenoma development, whereas classic ACF, with elevated structure, hyperplasia and normal beta-catenin level, are probably not.The expressions of peroxisome proliferator-activated receptors (PPARs) beta/delta, cyclin D1 and beta-catenin in ACF, adenoma and normal tissue from AOM-treated Apc(Min/+) mice and a familial adenomatous polyposis (FAP) patient colon tumour were assessed by immunohistochemistry and immunoblotting.The flat ACF (ACF(Min)) displayed increased cytoplasmic levels of beta-catenin, and increased levels of cyclin D1 and PPARbeta/delta. In contrast, the expression in classic ACF resembled normal mucosa. Adenomas from Apc(Min/+) mice, as well as a FAP patient colon tumour, displayed increased nuclear and cytoplasmic levels of beta-catenin, and the same expression patterns of cyclin D1 and PPARbeta/delta as those found in flat ACF.In addition to activation of the Wnt signalling pathway in both flat ACF and in adenomas in Apc(Min/+) mice, the increased expression of PPARbeta/delta in these lesions could be a target for pro-inflammatory signals important for growth and reduced apoptosis.