Purpose Self-poisoning occurs with over-the-counter (OTC) drugs, particularly paracetamol (acetaminophen). In 1998, OTC pack sizes of paracetamol were reduced. We have studied the effect of this pack size restriction on OTC supply of paracetamol, aspirin and ibuprofen. Methods IMS Health UK provided data on the UK sales of paracetamol, aspirin and ibuprofen. The total mass and number of packs of each drug supplied were compared for the years 1998, 1999 and 2000. Results The mass of aspirin and paracetamol sold fell, that of ibuprofen increased. The number of paracetamol packs sold was unchanged, the analgesic dose of aspirin fell and ibuprofen supply increased. Conclusions It seems that the paracetamol pack size reduction has not achieved as large an overdose rate reduction as might have been expected. Instead, a shift to the use of ibuprofen may lead to an increase in gastrointestinal adverse events and continue the burden on healthcare resources. Copyright (C) 2002 John Wiley Sons, Ltd.