An oral electrolyte solution containing 125 mM/L sodium, 10 mM/L potassium, 80 mM/L sulfate, 20 mM/L bicarbonate, and 80 mM/L of polyethylene glycol, and associated with little water or electrolyte absorption from the gut was recently described in this journal. To determine the efficacy of this solution (Golytely) for colonoscopy, 20 consecutive patients were randomized to either a standard colonoscopy prep or Golytely. Both preps resulted in a feces-free colon, allowing colonoscopy to the cecum in most cases. Although Golytely produced mild cramps (3 of 12) and transient fullness (6 of 12 vs. 0 of 8 with standard prep, p less than 0.02), 11 of 12 were willing to repeat Golytely vs. 3 of 8 with the standard prep (p less than 0.02). It is concluded that Golytely is an effective prep for colonoscopy and well tolerated by patients. It is especially useful for those requiring repeated examinations because of patient acceptance and efficacy.