1. Cisapride is a novel prokinetic drug which facilitates or restores motility throughout the gastrointestinal tract. Its mechanism of action is thought to involve enhancement of acetylcholine release in the myenteric plexus of the gut. 2. The effect of intravenous cisapride 10 mg on gastro-oesophageal dysfunction was investigated in 20 patients with systemic sclerosis, using a double-blind, randomised, cross-over, placebo-controlled manometric study design. 3. The increase in lower oesophageal sphincter pressure was significantly higher after cisapride (mean +/- s.e. mean, 8.3 +/- 2.1 cm H2O) than after placebo (mean +/- s.e. mean. 0.1 +/- 0.3 cm H2O) (P less than 0.001). The increase in the number of fundic gastric contractions during the 30 min study period was significantly higher after cisapride (mean +/- s.e. mean, 7.7 +/- 2.3) than after placebo (mean +/- s.e. mean, 0.9 +/- 0.6) (P less than 0.01). 4. No serious clinical adverse effects were observed. 5. The study demonstrates that intravenous cisapride induces a significant increase in lower oesophageal sphincter pressure and in the number of fundic gastric contractions, which may be beneficial in the treatment of scleroderma gastro-oesophageal dysfunction. Further long-term studies of the effect of oral cisapride in patients with systemic sclerosis are warranted.