Background: The embryonic pancreas has, during recent years, proven to be an excellent system for the study of development and differentiation. There are many studies about pancreas structure while few numbers of quantitative or embryological studies were dealt with pancreas. Aim of the wok: The aim of this work was to evaluate the structural and proliferating features of pancreatic tissue during the prenatal and postnatal development of albino rat pancreas. Material and methods: 25 virgin female and 10 male albino rats (200-250 g) were obtained from the animal house, Faculty of Medicine, Zagazig University. After mating and pregnancy, the rat embryos and offspring were divided into groups and subgroups; Group A (16th&20th fetal rats), Group B (1st, 3rd, 7th 14th&21st postnatal days rats) and Group C (3 month old adult rats).The fetal rats were fixed as whole or dissected while the postnatal and adult rats were decapitated and dissected to obtain pancreas which was processed for light microscopic examination, morphometric and immunohistochemical studies. Results: In late prenatal and postnatal days, the duct system resembled those of adult except the intralobular ducts were close to developed islets while in adult age, were between the acini. The histological study revealed changes in the number, size, lumen of acini and acinar cell volume or in distribution of zymogen granules of acinar cells. Endocrine cells were scattered then aggregated in islets with irregular architecture till reaching regular mature adult form. Immunohistochemistry and morphometric studied revealed significant decrease in the proliferation of pancreatic tissues with advance of age. The percentage of endocrine cells per field area was significantly increased from ED16 to PD1 followed by high significant decrease from PD1to adult age. The number of β- cells per field area was significantly increased from ED16 to PD7 followed by non-significant increase from PD7 to PD21 then was highly significant decreased towards adult age. The diameter area occupied by β- cells within the islets increased gradually From ED16 to adult age and they were always aggregated in the central core of islet especially in the postnatal age groups. Conclusion: The study concluded that the pancreas undergoes differentiation and maturation during late prenatal and early postnatal ages including both exocrine and endocrine parts.