Continuous cell lines have been isolated from islet cell, small cell anaplastic and acinar cell carcinomas arising in the pancreas of transgenic mice, line Tg(Ela-1-SV40E)Bri18. These mice carry the pseudogene construct composed of elastase-1 promoter linked to the SV40 T antigen. Cells derived from islet cell or small cell anaplastic tumors secreted insulin and somatostatin during the early period of culture. Phenotypic alterations occurred during culture, whereby insulin secretion ceased and cells instead secreted somatostatin, indicating a change from beta-cell to delta-cell phenotype. Acinar cell lines did not secrete amylase or lipase.