In Denmark the only registration of the number and type of drug overdoses handled by the Danish health care system is the record of treatments in Denmark performed by the National Patient Registry (Landspatientregistret). Unlike other poison control centres, the Danish poison control centre handles only calls from health care personnel. An analysis of the records in the Danish Hospital Discharge Registry over a six-year period revealed that although most of the cases had probably been recorded, ATC codes were missing in half the cases. Furthermore, in 10-30% of the cases in which an ATC code was present, there was a conflict between the diagnosis and the ATC code. Unless the quality of the records in the National Patient Registry is improved, it will be impossible to carry out effective pharmaceutical vigilance in Denmark.