Seventeen patients have completed a double-blind cross-over study of hydrotalcite against placebo in the treatment of bile vomiting after surgery for peptic ulcer. Overall there was no significant difference between the two treatments, with 9 patients improving on hydrotalcite and 5 on placebo. The original operation had been peformed less than 3 years before the study in 9 patients; in this subgroup there was an improvement on hydrotalcite treatment in 8 patients but in only 1 on placebo. These differences are statistically significant (P less than 0.005). Nausea, vomiting, heartburn and epigastric tenderness were improved although gastritis and endoscopic changes were not affected. It appears that hydrotalcite can help palliate symptoms of bile vomiting occuring soon after surgery for peptic ulcer.