Antacids have served us well for over a century. In terms of peptic ulcer disease, the attitude in the late 1950s to 1970s that antacids should be taken only on demand was unjustified and erroneous. 13 recent endoscopic controlled studies have confirmed the efficacy of antacids in the healing of duodenal ulcer, achieving about 75% healing in 4 weeks. The efficacy of antacids in promoting gastric ulcer healing has been less well studied and the results are controversial. The most appropriate and economical antacid regimens for the treatment of duodenal ulcer disease should include tablets or liquid that have acid neutralising capacity of 400 mmol/day given at least an hour after meals. As a long term therapy, antacids appear to work, but need be taken in multiple daily doses, a regimen which is unlikely to meet with long term patient compliance. Patients with gastro-oesophageal reflux disorders or pregnancy-related reflux have also benefited from the usage of antacids ad libitum. Early previous studies have clearly demonstrated the efficacy of antacids in reducing gastro-oesophageal reflux and healing of reflux oesophagitis. The acidity of the gastric contents is the major determining factor in the outcome of the aspiration pneumonitis occurring during delivery. The prophylactic use of antacids during delivery has helped to reduce the severity of this complication. Similarly, the prophylactic administration of antacid aiming to maintain gastric pH between 3.5 to 7.0 has resulted in significant reduction of bleeding due to stress associated ulcers and/or erosive haemorrhagic gastritis in critically ill patients. Antacid therapy, however, is controversial in the management of nonulcer dyspepsia or nonsteroidal anti-inflammatory drug related upper gastrointestinal mucosal damage. Undoubtedly, antacids have major roles to play in the treatment of gastric acid related disorders. They have clear advantages and disadvantages when compared with the antisecretory agents. New proton pump inhibitors in particular have certainly superseded antacids and even the H2-receptor antagonists in many respects. However, the long term safety record of antacids remains unsurpassed by any of the new antisecretory agents.