A study was made of 187 patients suffering from overdosage by means of clinical records and drug analysis. Drugs were detected in 152 patients. The groups of drugs most frequently involved in these patients were sedatives (51-7%), tricyclic antidepressants (21-8%) and analgesics (11-2%). This overall pattern differed little from that determined by clinical diagnosis. However, discrepancies between clinical diagnosis and laboratory analysis were found in 43 patients. A retrospective assessment was made from clinical records of the influence of drug assay results upon clinical management. Decisions as to the need for admission to hospital and decisions relating to the management of patients suffering from overdoses of analgesics and tricyclic antidepressants were aided by drug analysis.