This experiment was carried out to investigate the influence of Aloe vera in the pancreatic islets of streptozotocin diabetic mice. Experimental diabetes was induced in ICR mice with a single injection of SZ (140mg/Kg body weight, ip). The mice demonstrating hyperglycemia 48 hours after SZ injection were treated for 16 days with Aloe vera (300, 800mg/Kg). Plasma glucose was measured, and for morphological studies of the islets specimens were staind with hematoxylin-eosin and by immunocytochemical methods. Then we observed the morphological changes of islets. Polymorphonuclear cells were infiltrated at the periphery of the islets 48 hours after SZ injection in SZ-treated ICR mice, but no prominent WBC infiltration was observed throughout the experiment. Blood glucose in mice treated with Aloe vera after SZ injection was higher than that of SZ injected mice, and mononuclear cells were heavily infiltrated at the islets 16 days after Aloe vera treatment (300mg/Kg), and significant islets infiltration of mononuclear cells was observed 30 days after Aloe vera treatment (800mg/Kg). Islets of ICR mice treated with Aloe vera after SZ injection showed severer insulitis, degranulation and necrosis of B cells than those of SZ injected mice. These studies indicate that Aloe in SZ injected mice increases vascular permeability and number of WBC in pancreatic islets, and potentiates destruction of B cells by cell-mediated immune system