The aim of this study was to prevent rejection after islet xenotransplantation. Islet obtained from Wistar Furth rats were macroencapsulated with agarose and collagen before transplanted into diabetic C57BL/6, B6AF1, and BALB/c mice. The results showed that the diabetic condition was reversed in 92.3% of recipients transplanted with macroencapsulated islets. The normoglycemic state of recipients was maintained 125.8 +/- 57.9 days without immunosuppression. The glucose tolerance curves in these mice were similar to those of normal mice. The macroencapsulated islets retrieved 103 days after transplantation showed no evidence of tissue reaction or fibrosis. These indicated that the macroencapsulated islets serve both to achieve and maintain normoglycemia of recipients, as well as to protect islet xenografts from rejection.