We assayed the estrogen receptors and polyamine levels (putrescine, spermidine and spermine) in the neoplastic and "normal" surrounding tissue of patients with colorectal cancer. Polyamine levels and the spermidine/spermine ratio were significantly higher in the neoplastic tissue than in the "normal" surrounding colonic mucosa of the same patients. Estrogen receptors were fewer in neoplastic mucosa than in the surrounding tissue, and polyamine levels were higher in estrogen-receptor negative tumours than in estrogen-receptor positive ones, although this was statistically significant only in the case of spermidine. Polyamine levels and estrogen receptor concentrations did not correlate with the tumour site, histological differentiation, or the age and sex of patients.