An obstacle to development of methods to quantify beta cell turnover from pancreas tissue is the lack of available conversion factors for the frequency of beta cell replication or apoptosis detected by immunohistochemistry to rates of replication or apoptosis. We addressed this in islets from one month old rats by quantifying the relationship between the rate of beta cell replication observed directly by time-lapse video microscopy (TLVM) and the frequency of beta cell replication in the same islets detected by immunohistochemistry (IHC) using antibodies against Ki67 and insulin in the same islets fixed immediately after TLVM. Likewise we quantified the rate of beta cell apoptosis by TLVM and then the frequency of apoptosis in the same islets using TdT-mediated dUTP nick-end labeling (TUNEL) and insulin. Conversion factors were developed by regression analysis. The conversion factor from Ki67 labeling frequency (%) to actual replication rate (%event/h) is 0.025 ± 0.003 (h-1). The conversion factor from TUNEL labeling frequency (%) to actual apoptosis rate (%event/h) is 0.41 ± 0.05 (h-1). These conversion factors will permit development of models to evaluate beta cell turnover in fixed pancreas tissue.