Objective To evaluate the effects of peritoneal rest on peritoneal transport and morphology in a rat model of peritoneal dialysis. Design Twenty-four rats (Sprague-Dawley, male, 250 300 g) were divided into three groups: group 1 (control, n = 6) without dialysis, group 2 (n = 9) sacrificed immediately after 3 weeks of dialysis, and group 3 (n = 9) sacrificed after 4 weeks of peritoneal rest after 3 weeks of dialysis. Both dialysis groups were dialyzed twice daily with an intraperitoneal instillation volume of 25 mL of 3.86% dextrose solution for 3 weeks. Peritonitis was induced by supplementing the dialysis fluid with lipopolysaccharide (5 μg/mL) on days 8, 10, and 12 in both dialysis groups. Peritoneal equilibration tests were performed on each animal at baseline. The equilibration tests were repeated at the 4th and the 8th week of dialysis. Morphometric analyses of the peritoneal membrane were carried out in tissue specimens obtained at the time of sacrifice. Results The DIDo ratio for glucose at two hours in groups 2 and 3 at the beginning of week 4 was significantly lower than at baseline, indicating an increase in peritoneal permeability to glucose after 3 weeks of dialysis. DIDo in group 3 at the beginning of week 8, after 4 weeks of peritoneal rest, was significantly higher than at week 4. The drain volume in groups 2 and 3 at week 4 was significantly lower than at baseline; however, the drain volume in group 3 at week 8 was significantly higher than at week 4. The thickness of the parietal peritoneal membrane in group 3 was significantly greater than in group 1 and less than in group 2 (group 1, 11.4 ± 7.6 μm; group 2, 37.5 ± 18.4 μm; group 3,21.4 ± 12.1 μm). Conclusions Peritoneal rest improves ultrafiltration in rats by decreasing the hyperpermeability of glucose and also reduces the degree of peritoneal thickening. These data suggest that dialysis -induced changes in peritoneal transport and morphology are reversible under the conditions of peritoneal rest in this experimental model.