Expression of Muc 1 mRNA was evaluated in normal and metastatic-tumor tissues obtained from a patient who died from extensive metastasis of a well-differentiated pancreatic adenocarcinoma. Northern blot analysis of total RNA from these tissues revealed that Muc 1 mRNA was detectable and unaltered in size in all metastatic tumor samples tested, including those from lymph node, liver, colon, and stomach. Southern blot analysis indicated that two forms of Muc 1 gene alleles were present in all normal and metastatic tissues of this patient with no evidence for gross rearrangement, deletion, or duplication.