Peritoneal dialysis is an alternative to hemodialysis in the treatment of patients with end-stage renal disease. Long-term use of peritoneal dialysis is limited by progressive alterations in the peritoneal membrane. The pathological changes in the peritoneum are due to the exposure to traditional nonphysiological peritoneal dialysis fluids that have low pH, high glucose and glucose degradation product content, and high molarity. Repeated episodes of bacterial peritonitis are another cause of peritoneal membrane damage. The characteristic features of peritoneal alterations include peritoneal fibrosis and morphologic changes in the peritoneal microvasculature with the accumulation of extracellular matrix in the submesothelial area and loss of mesothelial cells.These changes in the peritoneal membrane cause ultrafiltration failure and loss of dialysis efficacy. The pathogenesis of the peritoneal membrane damage is very complicated and understanding the processes involved in these alterations will be crucial in improving treatment with peritoneal dialysis. Some points of view on fibrosis of peritoneal membrane in patients undergoing peritoneal dialysis are presented here.