The expression of the human Muc 1 mRNA was evaluated during fetal pancreatic development. Human fetal pancreatic tissues were collected at various stages from 13 to 24 weeks of age. Northern blot analysis of total RNA from these tissues showed that Muc 1 mRNA was not detectable until 18-19 weeks of age. Therefore, Muc 1 mucin expression can be detected in prenatal human pancreata at approximately 19 weeks of age and thereafter.