Autologous implant of peritoneal mesothelium in rabbits and man. With the purpose of studying peritoneal physiology, original biopsy methods were devised and human and rabbit peritoneal mesothelial cells cultured and characterized. It was then decided to verify whether these cells could be implanted autologously during peritoneal dialysis in cases of acute loss of mesothelial surface. Staphylococcal peritonitis was induced in 12 rabbits and after 4 days of antibiotics, 6 of them were autoimplanted with cultured mesothelial cells, previously marked in 3 cases with thymidine (H3TdR). Implanted rabbits sacrificed after 3 and 6 days showed taking of the new mesothelial cells both by direct morphological observation and by autoradiography. Four uremic CAPD patients recovering from severe peritonitis were implanted with 300 million of their own peritoneal mesothelial cells, previously cultured and frozen. Morphological signs of taking were evident by laparoscopy and from peritoneal biopsies performed 3 and 6 days after implant. The fact that such implants are possible may have interesting applications in medicine and surgery. 