Two cases of papillary cystic tumor (PCT) of the pancreas were investigated for the presence of estrogen receptors (ERs) and progesterone receptors (PgRs). Both PCT and normal pancreas are able to specifically bind 3H-estradiol. This binding almost exclusively results from the presence of high levels of type II ER, whereas type I ERs were absent or present at very low levels. Both normal and neoplastic pancreas studied immunohistochemically for the presence of nuclear ER had negative results. This could be explained assuming that anti-ER antibodies are specific for type I binding sites. In conclusion, the presence of specific estrogen as well as progesterone binding may explain the sex and age predilection of PCT and suggest a possible hormone sensitivity for this tumor.