Every occasion when a patient is exposed to a medical product, is a unique situation and we can never be certain about what might happen.An adverse drug reaction (ADR) has recently been defined as ‘‘An appreciably harmful or un- pleasant reaction, resulting from an intervention related to the use of a medicinal product, which predicts hazard from future administration and warrants prevention or specific treatment, or alteration of the dosage regimen, or withdrawal of the product ’’. Pharmacogenomics may be one of the most immediate clinical applications of the Human Genome Project8 and may become part of standard practice for “quite a number of disordersand drugs by year 2020.”Recent developments in technology and bioinformaticspermit the rapid assay and interpretationof 25 000+gene transcripts on smallsolid-state ‘chips’This approach has the advantage of sensitivity, in that very low levels of transcripts can bemeasured, but has some significant limitations.Proteins can be measured reliablyin a broader range of biological tissues (e.g.blood, CSF, synovial fluid) than mRNA transcriptsand are the ‘business molecules’. On thenegative side, it is more difficult to detect proteinsexpressed in low abundance. Moreover, for theinvestigation to enter clinical practice, a rapidassay of protein markers is required. However,once the biomarkers that characterise a drug responsehave been identified, these proteins couldbe screened by standard immunoassay.Adverse drug reactions (ADRs) have been monitored in many countries since the beginning of the1960s in a so-called ‘early warning’ function to collect knowledge about ADR profiles in order to acquire information on serious, rare and unknown ADRs at an early stage.Periodic evaluation of ADRs reported in a hospital helps in characterizing the pattern of ADRs and thereby help in designing steps to improve the safety of drug use in the working set up.It is only through the use of efficient, timely, cost-effective use of computerized clinical databases based on the EMR, that we have been able to detect errors in the delivery of medications in patient care. The use of computer-based decision support tools based on EMR in the management of ADE and other clinical situations have been shown to improve day to day patient care, improve the quality of care and outcomes as well as reduce health care costs .