The present study concerns the influence of the transplantation of free and encapsulated (AN69 membrane, Hospal) islets on the chemotaxis of peritoneal macrophages. Fifty free or encapsulated rat islets, cultured for 24 h, were transplanted in the peritoneal cavity of mice (n = 12). Three days after transplantation, the chemotaxis of peritoneal murine macrophages was tested towards formyl-methionyl-leucyl-phenylalanine (fMLP) and a culture medium conditioned for 3 days by free rat islets isolated from the same rat donor. In response to fMLP, the chemotactic indexes of macrophages from mice transplanted with free or encapsulated islets were 8.09 +/- 2.10 and 9.45 +/- 2.76, respectively. These values were significantly higher than those obtained when macrophages from untreated mice were tested (2.42 +/- 0.23; p < 0.01). In response to culture medium conditioned by free islets, the transplanted encapsulated islets failed to enhance macrophage chemotaxis (2.41 +/- 0.53) compared to transplanted free islets (7.00 +/- 2.63; p < 0.01). Thus, encapsulation decreased the specific chemotactic activity of peritoneal macrophages induced by free islet transplantation, probably by prohibiting the diffusion of chemoattractants.