We evaluated the efficiency of polyethylene glycol at low dosage for the treatment of chronic constipation. A prospective, randomized, double blind study was performed in 34 patients (32 female, 2 male) with the following inclusion criteria: age between 20-60 years, history of more than 5 years of constipation and no lower endoscopic findings of infections or malignancies. The solution was administered in a fasting state at the rate of 0.5 liters daily during 8 days. Patients were divided in 2 groups. Group 1 received placebo during the first week and PEG during the 2nd. week. Group 2 received PEG solution during the first week and placebo during the 2nd. A mean of 5.53 bowel movements was observed after placebo and 12.13 after PEG in group 1 (p < 0.005). A mean of 13.56 bowel movements were observed in group 2 after PEG and 7.73 after placebo (p < 0.001). Decreased consistency of the stools was seen after PEG in both groups (p < 0.001). According to our findings, low doses of PEG were useful and safe in the treatment of constipation, with few side effects.