To evaluate the efficacy of a polyethylene glycol electrolyte solution (PEG-4000) in pregnant women affected by constipation, 40 consecutive pregnant women from 6 to 38 weeks' gestation were enrolled in this preliminary study. Constipation was defined as spontaneous evacuation less than four times a week or the presence of symptoms such as defecation pain, rectal urgency, tenesmus, anal injury, or abdominal pain. A PEG-4000 solution (Isocolan, also marketed in the United States as Golitely/Nulitely) was administered for 15 days at a dose of 250 mL by mouth once or twice a day. The number of bowel movements per week, the presence or absence of liquid stools, tenesmus, urgency, defecation pain, anal lesions, and abdominal pain were evaluated before and after 15 days of treatment. Treatment with PEG-4000 significantly increased the evacuation episodes per week (from 1.66 ± 0.48 to 3.16 ± 1.05; P <.01), and constipation was resolved in 27 of 37 women (73%). Defecation pain, anal injury, and abdominal pain significantly improved after PEG-4000 administration. Improvement occurred in both patients with new-onset constipation during pregnancy as well as patients with a history of constipation before pregnancy. These preliminary findings indicate that PEG-4000 may be an effective choice for the treatment of constipation during pregnancy.