Background and aims: Conservative therapy for patients with acute colonic pseudo obstruction (Ogilvie’s syndrome) may be successful initially but relapses are common. The aim of the present study was to evaluate the effect of polyethylene glycol (PEG) electrolyte balanced solution on the relapse rate of the syndrome after initial resolution with neostigmine or endoscopic decompression. Patients and methods: The study was performed on 30 consecutive patients who presented with abdominal distension and radiographic evidence of colonic dilation, with a caecal diameter ≥10 cm, that resolved conservatively. Patients then were randomised to receive daily 29.5 g of PEG (n = 15) or similar placebo (n = 15). Patients were monitored daily for a seven day period for stool and flatus evacuations, and colonic diameter on abdominal radiographs. Administration of the test solutions and assessment of patient symptoms and x rays were performed in a blinded fashion. A caecal diameter ≥8 cm with a concomitant≥10%increase after initial successful therapeutic intervention was considered as a relapse and these patients, after a second therapeutic intervention, were eligible to receive open label PEG. Results: Twenty-five patients received neostigmine as the initial therapeutic intervention which resulted in resolution of colonic dilation in 88%of cases. Eight patients had successful endoscopic decompression. Five (33.3%) patients in the placebo group had recurrent caecal dilation compared with none in the PEG group (p = 0.04). Therapy with PEG resulted in a significant increase in stool and flatus evacuations (p = 0.001 and 0.032, respectively) as well as in a significant decrease in the diameter of caecum, ascending and transverse colon, and abdominal circumference (p = 0.017, 0.018, 0.014, and 0.008, respectively). Conclusions: Administration of PEG in patients with Ogilvie’s syndrome after initial resolution of colonic dilation may increase the sustained response rate after initial therapeutic intervention. Background and aims: Conservative therapy for patients with acute colonic pseudo obstruction (Ogilvie’s syndrome) may be initially initially but relapses are common. The aim of the present study was to evaluate the effect of polyethylene glycol (PEG) electrolyte balanced solution on the relapse rate of the syndrome after initial resolution with neostigmine or endoscopic decompression. Patients and methods: The study was performed on 30 consecutive patients who presented with abdominal distension and radiographic evidence of colonic dilation, with a caecal diameter ≥ 10 cm, that resolved conservatively. were randomized to receive daily 29.5 g of PEG (n = 15) or similar placebo (n = 15). Patients were monitored daily for a seven day period for stool and flatus evacuations, and colonic diameter on abdominal radiographs. Administration of the test solutions and assessment of patient symptoms and x rays were performed in a blinded fashion. A caecal diameter ≥8 cm with a co ncomitant≥10% increase after initial successful therapeutic intervention was considered as a relapse and these patients, after a second therapeutic intervention, were eligible to receive open label PEG. Results: Twenty-five patients received neostigmine as the initial therapeutic intervention which resulted in resolution Five patients had the successful endoscopic decompression. Five (33.3%) patients in the placebo group had recurrent caecal dilation compared with none in the PEG group (p = 0.04). Therapy with PEG resulted in a significant increase in stool and flatus evacuations (p = 0.001 and 0.032, respectively) as well as in a significant decrease in the diameter of caecum, ascending and transverse colon, and abdominal circumference (p = 0.017, 0.018, 0.014, and 0.008, respectively) . Conclusions: Administration of PEG in patients with Ogilvie’s syndrome after initial resolution of colonic dilation may increase the sustained response rate after init ial therapeutic intervention.