Telomerase activity (TA) and telomerase reverse transcriptase (rTERT) were investigated in Sprague-Dawley rats, killed at 6 and 12 h, and 1, 2, 3, 7, and 14 days after 90% pancreatectomy (px), by TRAPeze enzyme-linked immunosorbent assay telomerase detection and reverse transcriptase-polymerase chain reaction. TA increased at 2 days and reached a maximum at 3 days after px, when the small ductules showed the highest proliferation activity. After 3 days, TA decreased to basal levels as the ductules differentiated into new endocrine and exocrine pancreas. The expression of rTERT showed a correlation with TA. These results suggest telomerase is actively regulated during pancreatic regeneration.