This study was performed as two consecutive experiments. In the first experiment, normal avian pancreas histology of adult hens was investigated histologically and histochemically. Exocrine part was acinar in nature with their pyramidal epithelial cells. Apical portions of the cells filled with zymogenous granules. Intermediate ducts lined up with simple squamous epithelium were frequently encountered among the acini. In the second experiment, endoenne cells were destroyed by giving intravenously 5% w/v solution of alloxan (Alloxan tetrahyrate-Merck) at a dose of 250 mg/kg body weight. The blood sugar level sharply increased up to 315.7 mg/100ml at the first hour, and by gradual increase, reached at its highest level which is 396,8 mg/100ml at the 28th hour following alloxan administration. In non-treated, normal animals, the levels were between 180-260 mg/l00ml. The zymogenous granules disappeared at the first hour after treatment as demonstrated in the sections stained with Gomori's chrome alum haemaloxylin-phloxine technique. Beta cells at the endocrine islands displayed typical degranulation together with nuclear pyenosis and karyolisis those continued until 48 Ih hour following alloxan adminislration. Delinile cellular changes were observed in the acinar epit-helta around Ihe degenerating islands beginning at the 5th hour after the treatment. The changes continued with the appearance of basophilic granules in Ihe acinar cell cytoplasm while they were gaining more spherical shape. Blood sugar level dropped back to the normal level (222 mg/100ml) after 48 hours. Acinar epithelial cells were observed in the islands among the degenerated endocrine cells one week after the treatment. This was more frequently seen at later periods and was interpreted as a regeneration occured by transformation ot acinar epithelia into beta cells.