Pancreatic β-cells in the islets of Langerhans secrete insulin in response to the rise in glucose levels following food intake. The hypoglycemic action of insulin applies a strong evolutionary brake on β-cell division. However, under some conditions β-cells can be stimulated to enter cell cycle progression and divide, for example following exposure to increased glucose levels or during pregnancy. Here, a protocol is described for the isolation of rat adult islets of Langerhans, followed by culture of intact islets in Matrigel and measurement of β-cell replication by the incorporation of ethynyldeoxyuridine (EdU). EdU positive cells are revealed by a click reaction, nuclei are visualized using a DNA-binding fluorophore (Hoechst 33342), and β-cells are identified using immunofluorescence detection.