Many acutely poisoned patients are treated with no laboratory help other than general clinical chemistry and haematology. Emergency toxicological analyses (24-hour availability) that could influence immediate patient management such as iron, lithium and paracetamol (acetaminophen), are relatively few in number and are remarkably similar worldwide. These assays should be provided at hospitals with large accident and emergency departments. More complex, less frequently needed clinical toxicological assays that can often be offered on a less urgent basis are usually provided from regional or national centres because of the need to make best use of resources. Recommendations as to the assays that should be provided locally and at regional centres are available for the UK and US, and are generally applicable. Regional centres normally diversify into specialised therapeutic drug monitoring, urine screening for drugs of abuse, metals analysis and sometimes forensic work in order to widen the repertoire of tests available and to increase funding. Whatever the type and quantity of work undertaken and the instrumentation used, guidelines are now available delineating staff training, method validation, assay operation, quality control/quality assurance, and indeed virtually all other aspects of laboratory operation. These considerations notwithstanding, clinical interpretation of analytical results remains a difficult area and is the responsibility of the reporting laboratory, at least in the first instance.