Recent experimental and clinical pharmacological studies on colloidal bismuth subcitrate (CBS) are reviewed. CBS combines with mucus to produce a marked retardation of the movement of hydrogen ions. CBS has potent anti-ulcer and anti-erosive action in various experimental models in animals, and is able to stimulate the generation of gastric mucosal prostaglandins. CBS is thought to be a cytoprotective agent. The type of mucosal cell repair in the vicinity of the ulcer is favourably affected in man. CBS also exhibits anti-pepsin and bile acid-binding properties. Pyloric campylobacter are inhibited in vitro and in vivo. The recent pharmacological findings are discussed in the light of the clinical efficacy of CBS and new indications.