Pericapsular macrophage infiltration of alginate-poly-L-lysine-alginate (A-P-A) microencapsulated islets was thought to be one of many factors that resulted in graft failure. In this study, 15-deoxyspergualin (15-DSG) was used to study its effect on pericapsular cellular infiltration and graft function of A-P-A microencapsulated islets. Normal male BALB/c mice were used as recipients to receive 200 A-P-A microencapsulated rat islets intraperitoneally and divided into three groups. Mouse in group B and C received 1.25 and 2.5 mg/kg body weight/day of 15-DSG, respectively, via a subcutaneous Alzet osmotic minipump for 4 weeks. Mouse in group A received normal saline as the control. At the end of 4 weeks, implanted islets, peritoneal monocytes were retrieved for morphologic and functional evaluations.Our data suggested that 15-DSG attenuated pericapsular macrophage infiltration and preserved graft function of A-P-A microencapsulated rat islets in normal BALB/c mice.