In 1994, in the UK, histamine-2-receptor antagonists (H2RAs) were switched from prescription to non-prescription, over-the-counter (OTC) status. However, the impact of this change has not been studied. OBJECTIVE: The objective of this analysis was to evaluate the effects of the change from prescription to OTC on sales of gastrointestinal products (GIPs). METHODS: IMS provided market sales in dollars and prescription volume for GI products from 1992 to 1997. All sales figures were converted to 1997 US dollars using the Consumer Price Index. RESULTS: Between 1992 and 1997, total spending on GIPs increased from $1.09 billion to $1.46 billion. Concurrently, spending on prescription GIPs rose from $940 million to $1.33 billion with a steady increase in number of prescriptions for GIPs to 22.2 million by 1997. Since the introduction of OTC H2RAs in 1994, their market share amongst all H2RAs has grown modestly from 0.9% to a high of 1.5% in 1996, when sales were approximately $7.2 million. The market share of OTC H2RAs amongst total OTC GIPs reached a high of 0.56% in 1995. CONCLUSION: The status change of H2RAs to OTC status has had a minimal effect on the OTC GIPs sold in the UK.