- Background. Long-term peritoneal dialysis (PD) is associated with peritoneal fibrosis and loss of function. It has been shown that activation of the adenosine A2A receptor (A2AR) promotes tissue repair, wound healing and extracellular matrix (ECM) production. We have previously shown that adenosine is a potent regulator of inflammation in the peritoneum. In the current study, we explored the role of adenosine and the A2AR in two experimental models. Methods. Collagen deposition was evaluated in primary peritoneal fibroblasts following treatment with an A2AR agonist and antagonist. In addition, peritoneal fibrosis was induced by i.p. injection of either chlorhexidine gluconate for2weeksor4.25%glucoseperitonealdialysisfluid(PDF) for 1 month. The development of fibrosis was compared between wild-type (WT) and WT mice treated with caffeine (an A2AR antagonist) in drinking water or between (A2AR +/+ ) mice and A2AR-deficient mice (A2AR −/− ). Results. Adenosine or the A2AR agonist CGS21680 stimulated collagen production by peritoneal fibroblasts in vitro and A2AR antagonists (ZM241385 and caffeine) blocked this effect. Consistent with these results, caffeine-treated WT or A2AR −/− mice had reduced submesothelial thickness, collagen deposition and mRNA levels of fibroblastspecificprotein(FSP-1)andconnectivetissuegrowthfactor (CTGF). In addition, treatment with caffeine in vitro and in vivo diminished A2AR and A2BR mRNA levels induced by CG or PDF while it upregulated A1 Rl evels. Conclusion. Our data suggest that adenosine through its A2AR promotes peritoneal fibrosis and therefore should be considered as a target for pharmacological intervention.